JEX NOEX JVPC.pdf

Complement for PetroVietnam University

e

X Nip- on 011I« Gas Exp ora ·on

JX Nippon Oil & Gas Explorat'ion

Contents of Guide Line for Training in NAKAJOGas & Oil Field

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Chapter 1 : Over view of Nakajo Oil & Gas Field of JX Nippon Gas & Oil Exploration Corporation 1.1 History 1.2 The Current Situation 1.3 Organization of Nakajo Oil & Gas Filed Office

Chapter 2 : The Characteristics of Non-AssociatedNatural Gas & Oil (NANG) 2.1 Stratigraphic Successions 2.2 Geological Structure 2.3 NANG Reservoir 2.4 Production System for NANG 2.5 Production Facilities for NANG

Chapter 3 : The Characteristics of Natural Gas Dissolvedin Water (NGDW) 3.1 Stratigraphic Successions 3.2 Geological Structure 3.3 NGDWReservoir 3.4 Production System for NGDW _/

3.5 Production Facilities for NGDW

Chapter 4 : The Characteristics of Shiunji Crude Oil 4.1 Stratigraphic Successions 4.2 Geological Structure 4.3 Shiunji Oil Reservoir 4.4 Production System for Shiunji Oil Field 4.5 Production Facilities for Shiunji Oil Field

Chapter 5:Instrumentation Network 5.1 Comprehensive Instrumentation and Control Computer System (CENTUM) 5.2 Telemeter System

Contents-1

JX Nippon Oil It Gas Exploration

5.3 Telecommunication Cable Network 5.4 Power Supply Chapter 6: Measurement and Control Instruments 6.1 Measurement Instruments 6.2 Control Devices Chapter 7: Automatic Systems 7.1 Monitoring 7.2 Control 7.3 Daily Report Chapter 8: Well Drilling, Workover, Well Service 8.1 Reviewof

NK-66 (NANG),N21-5,6 &7 (NGDW)and NK-67(NANG)

8.2 Workover 8.3 Well Services Chapter 9 : Facility Maintenance of Nakajo Gas & Oil Field 9.1 Facility Maintenance Control 9.2 Facility Maintenance, Repair & Replacement Chapter 10: Iodine Factory in Nakajo Oil & Gas Field 11.1 Characteristics of Iodine 11.2Various Uses ofIodine 11.3 Production ofIodine

in the world, Japan and Nakajo field

11.4 Production Facilities ofIodine Factory

Appendix 1: HSE of Nakajo Gas & Oil Field Chapter 1: HSE rule of the Nakajo Oil and Gas Field Chapter 2 : Operational Safety Rule Chapter 3: PDCAfor safety of the Nakajo Oil and Gas Field Chapter 4: Others. Appendix 2: Drilling Program for Well, NK-67

Contents-2

0t

Appendix 3:Industrial

Measurement

JX Nippon Oil & Gas Exploration

and Process Automation

Chapter 1 : Electromagnetic Flowmeter Chapter 2 : Orifice Plate Flow Measurement Chapter 3 Other Flow Measuring Devices Chapter 4: Temperature Measurement Chapter 5: Pressure Measurement Chapter 6: Liquid Level Measurement Chapter 7: Control Valves and Actuators Chapter 8: Gas Chromatography Chapter 9: Telemetry:Application

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Note) Chapter 1 and 2 will coverfor the first day oftraining period, Chapter 3 and 4 will be for the

2nd day,

Chapter 5-7 will be for the 3rd day, Chapter 8 and 9 will be for

the 4th day, and Chapter 10 and 11 will cover for the final day. However, this schedule will be changed according to the actual progress.

Contents-3


Chapterl Overview of Nakajo Oil & Gas field of JX Nippon Oil & Gas Exploration Corporation 1.1 History The history of Nakajo oil/gas field(refer to attached location map) dates back to the discovery of the NGDW(natural gas dissolved in water) reservoir with the drilling of the R-l well at Muramatsuhama in Nakajo - town in 1957. This success spurred further activity along the coast line to exploit the NGDWfield and production commences in1961, by which time 15 bases, 54wells and both the North and South processing stations and the pipe line to Nakajo - town has been constructed. While exploitation of the NGDW continued, a gravity survey was started throughout the whole kita-Kambara plain in 1958, Followedby seismic surveys. In the stretch between Tsuiji and Seiro since 1959. As a result, an anticline structure was discovered near Tsuiji-Nagaike, and after further geological study, an exploratory well, NK-l, was drilled there in 1961. In addition, a NANG(non-associated nature gas) reservoir was discovered un the Shiiya Formation(Central district), followedin 19.65by a large reservoir which was discovered by NK-13 well at the north extension of the anticline (North district). Thus, by 1967, 11wells in the Central district and 13 wells in the North district were completed. As a result, in 1969 the Nakajo gas field produced a daily production of 1 million Sm3 of natural gas and 150kl of crude oil to become the major gas field in Japan. Subsequently, NK-53 well was drilled successfully into a new oil reservoir in the Shiunji district in 1978 and, although development and production soon followed, the production stopped in 1982(Details of the Shiunji district are not included in this text).

1.2 The Current Situation The Nakajyo gas field is located near the coast in a calm place surrounded by pine groves 7 km West of Central Nakajo-town. The operational field extends throughout a ranging 12 km North-South and 2km ' East-West and has facilities which include the producing 14 wells of the NGDW field along the coast, producing 9 wells in the NANG field inland, producing 2 wells in Shiunji district, 3 processing stations (Central, South and North), oil storage tanks, a central control room, substations and etc. Natural gas, mainly in the form of products, is supplied to Mizusawa Chemistry's

1-1


Nakajo factory and Shibata Gas Corporation etc. Crude oil is sent to INPEX Corporation and interstitial water which is produced from the NGDW reservoir, it supplied to the Iodine Factory in Nakajo Oil & Gas Field. A computer control system was installed in the early stages, enabling the production wells and the other facilities to be operated by a small number of operations. In the current, three wells(N21-5,6&7)in the NGDWhad been drilled in 2014, the productivity of these wells is 35,000 Sm3 to 50,000 Sm3, respectively. As a further, one producer, this well NK-67, in NANGfield would be drilled in 2015 in order to contribute for the production rate in Nakajo. 1.3

Organization of Nakajo Oil & Gas Filed Office

ADMINISTRATION SECTION

Administration Accounting

General Manager

PRODUCTION SECTION

HSE/ISO Staff

---i Facilities/Pipeline

Maint. Gr.

I

NGDW Operation Gr. NGDW: Natural Gas Dissolved in Water

CPS lOPS Operation Gr. cps: Central

Processing SI. OPS: Oil Processing SI.

Drilling I Wireline Gr. Electrical/Electronics Maint. Gr. Iodine Factory Gr.

1-2


Location Map

•

Nakajo Oil/Gas Field is Located about 300 km North of Tokyo and about 40 km North-East of Niigata City. • Gas/ Oil Concession Area is 12 km Nort to South and 2 km West to East. • Natural Gas: is shipped by pipeline as a raw material for city gas and industrial fuel. • Crude oil: is shipped to Oil Terminal Naoct u in tank lorry. • Brackish Water: is extracted the iodine a d the iodine sells (Kan·sui) abroad mainly as pharm ceutical raw materials. ( Iodine business) and supplies close spas hot spring w ter as part.

...

I

o • •

~

To User,

NANG: Non-associated Na u al Gas CPS:Central ProcessingSt tion NPS:North ProcessingStation OPS:Oil ProcessingStation SPS:South ProcessingStation

o

...r_

1

2

3

0#

....\-

--f

_s,~J-e_ .t

00 K",-_ (

f'f'

(

'M

\r~l' )

1 /(}\~

,"'\

r I--

I! ()

II

1-3

NANGWells NGDWWelis Oil Wells

4km


Chapter 2 : The Characteristics of Non-Associated Natural Gas & Oil (NANG) 2.1

Stratigraphic

Successions

The stratigraphic succession of the Nakajyo gas field are shown in Table 2.1-l. The main feature of each formation .are as follows; , (1) Basement complex The basement rocks of this area are composed of hornfels of the Palaeozoic era and granite rocks of the Mesozoicera (Cretaceous period). The hornfels, which was conformed at a depth of 3,014m in the NK-27well, show a slaty fabric. (2) Tsugawa Formation This formation distributes at the margin of the basement complex of the hinterland and is mainly composed of coarse sediments such as arkose and conglomerates etc. (3) Nanatani Formation This formation is predominantly composed of dark grey or black mudstone. However, in some areas, acidic volcanic activity is found in the under part of this formation and acidic rocks, such as dacite and rhyolite, or pyroclastic rocks are distributed. These volcanicrocks are called "green - tuff'. Al though "green - tuff' activity is not found in the North district of the Nakajyo gas field, these activities were conformedat a depth of 2,850m in the NK-28well in the Central district. (4) Teradomari Formation This form is mainly composedof dark grey or black mudstone partly intersesting the dandy tuff, and conformablyoverlies the Nanatani formation. (5) Shiiya formation In the hinterland, this formation is composed of dark grey mudstone, and is difficult to distinguish from the rock facies of the Teradomari formation. As it is overlaid unconformably by the Nishiyama formation, most of this formation has been eroded. However,in some places in this gas field only 5 or 6 km from hinterland, there is 2-1


an enormous of sediment marking up a formation over 1,OOOm thick. Sandstone intercalated in this formation might be turbidite. In the Nakajo gas field, we can recognize three different facies in this formation characterized by alternation of sand and mud. The lower part prevails mostly in the 'Central district and forms a sand-rich alternation, mainly composed of relatively coarse sandstone which mixes gradually into the surrounding mud-rich alternation. The middle part is composed of an alternation of tuff or fine sandy tuff and dark grey mudstone, and it is uniformly distributed all over the gas field. The upper part prevails mostly in the North district and is composed of a sand-rich alternation with tuffaceous sandstone prominent. This alternation gets gradually richer in mudstone towards the Central district. The Shiiya formation in south of the Central district, includes a lot of rock pieces, derived from the Teradomari formation or Nanatani formation, as can be distinguished by the difference in th~ fossil assemblage of the foraminifera. (6) Nishiyama formation This formation is composed mainly of dark grey or grey mudstone intercalating an alternation of pebbly tuffaceous sandstone and mudstone.

A sand-rich

alternation is developing predominantly in the area of the NGDW field along the coast situated at the west-wing of the anticline, with the thickness of the formation decreasing or diminishing toward the crest of the Tsuiji anticline. These sandstone formations, consisting of coarse or medium sand with gravel, are rather discontinuous and mostly distributed a lens-like form. The thickness of this formation becomes gradually thicker from east to west and local variation is also noticed. (7).Haizume formation This formation is composed mainly of grey-white or blue-white .siltstone, although parallel to the coast, some sand and gravel beds are distributed. It is difficult to distinguish this formation from the Nishiyama formation because

the lithofacies of Nishiyama formation chamges gradually into this formation, so that they should be differentiated depending on the change of foraminiferalfossil assemblage. (8) Uonuma group This group is quaternary, being largely composed of coarse sediment such as

----

---

2-2

0X JX Nippon Oil & Gas Exploration sand and gravel etc. It overlies the Haizume formation with unconformity. It is a fossil poor zone, and

slightly

intercalcated

with

lignite

bed, and is covered

extensively by sandhills and alluvium.

Table 2.1-1 Standard geological columnar section of Nakajo gas field Name of

fonna ion

Geologic; colUtM

Thickness

Gas of rese.r:voir formatiOfi m

Main

ithol

Light-brown medi\D sand, sand, 9ravel , clay

Gravel, sand,

130

±

300

± .mudstone,

clay,

silt

81ue grey ail

. one,

sandstone

t 0 0 N 0 C

k 01'4 0

>.

Q)

~

U

'-

co

.u

~ ,C7 >ID

Shi ya FOl:m~tion

.),.t

~ o z;

'""

Q)

t-

t 1

Grey mudstone, I 150

+ -

tuffaceous sandstone, conglcmerate

Alte.tnation of

1000:!: grey mXJstone tuffaceous sandstone

k

'6!> ~ CJ

t'er~do1'l\~r:i Formation

I'JI CJ k

·350

±

Black rrudsU:lne

500

±

Hard shale, tuff, dacite

2 00

±

Conglcrnerates.

,\) .2; 00( ;2;

Gra:nite

Hornfels

2-3

ark .r'


2.2

Geological Structure A part of the basement rocks of the Niigata sedimentary basin is exposed in the

Kushigata mountain range situated east of this gas field. A tertiary system on the west-wing of this mountain range are distributed under the plan with thickness increasing towards the south-west, generally near the center of the sedimentary basin. In the Kita-Kambara plain, several north-south trending structures are developing,and one of them forming a magnificent anticline deep under the Tsuiji area.This anticline is known as the "Tsuiji Anticline" and it extends continuously from north-northeast to south-southeast. The Tsuiji anticline generally has a steep inclination at its east-wing accompaniesby faults, and continuing in a zigzagwith some culmination. This gas field, being a part of an extensive anticline, ha~ separate culminations in its northern and central parts, so that structurally, it can be separated into two parts, called the North and Central districts. The North district is situated at the west-wing of north culmination. The inclination of the formation is 25 to 30° at the lower part of the Shiiya formation and 10° at the upper part of the Nishiyama formation. Therefore, the inclination changes gradually gentler towards the upper formation. In the Quaternary of Uonuma Group, a very gentle anticline is also noticed. The Central district is situated

III

the north and northwest of the southern

culmination and has similar tendency to the inclination of the formation in the North district. JX Nippon recognize a Saddle between both districts. The formations overlying the Shiya formation become thinner towards the axis of the anticline and the intercalated sandstone beds also show the same tendency. In the NGDWfield along the coastline, the volumetric ratio of sandstone bed increases and each formation above the Nishiyama formation is thick. Development of the Tsuiji Anticline was started in the Shiiya period, actively in the Nishiyama period, and completed in the Uonuma period through the Haizume period. The underground structure of the Nakajyo gas field is shown in Fig. 2.2-1 In addition, the Shiunji district which is situated at the west-wing of TsuijiAnticline has oil reservoir at the depth of 2,100m. The inclination of the formation is 25 to 30,° and it becomesdeeper towards the west-northwest, Gross reservoir thickness is 20 to 35 m and it shows a alternation of sand and mud.

2-4

JX 'Nippon Oil & Gas Exploration

Tainai

North district

Japan

Central district

Sea

field

H2G

•

line of

Ochibori River

Shiun)i district

NI(.152 OHK-48

•

Kaji River Branch

Fig. 2.2-1 Structural drawing of underground of Nakajo gas field (Top of Shiiya Formation.)

2-5


2.3

NANG (Non-Associated. Natural Gas) Reservoir The NANG reservoir is distributed

on the Tsuiji Anticline and consists of reservoir

rock with sandstone of the Nishiyama and Shiiya formations. The reservoir rock of the Shiiya formation is distributed and north wing of anticline

almost equally in the North district, but only in the west structure

in the Central

district and is thinned

out in

culmination. The trap of the North district is of the anticline district is a combination of the stratigraphic The reservoir of sandstone appearance

type, while that of the Central

and anticline types.

and pebbly sandstone in the Nishiyama formation has the

of stratigraphic

trap, while the reservoir rock of sandstone and tuff in the.

Shiiya formation can be said to be more of an anticline trap. The thickness of the reservoir shows a general tendency to be thin at the axis of the anticline and thick at the wing. This tendency is common to each formation

and each unit alternation,

which is

division of the reservoir. The drive mechanism

IS

a water drive, wherein

gas reservoir

pressure

declines

relatively slowly in relation to production, while gas/oil ratio changes very little. NANG reservoir is largely classified.by gas composition and gas oil ratio etc. into a dry gas reservoir

containing

mainly methane

at a depth of 510m to 1,130m in the

Nishiyama formation, a gas condensate reservoir at a depth of 1,590m to 2,000 m in the Syiiya formation, and an oil reservoir at a depth of 1,880m to 2,OOOmin the lower part of the Shiiya formation. The dry gas reservoir, which is related to the NGDW reservoir, is subdivided into 5 zories from zone 11to zone 15 in the Nishiyama formation. The gas condensate

and oil reservoirs

are similarly subdivided into a total of 10

zones of F to M and N. 0, respectively. Initial reservoir

pressure

corresponds

approximately

to depth with the exception

that zone Nand 0 of the North district are oil reservoirs with unusually high pressure. The temperature

gradient of the reservoir is the mean value of the Niigata district.

The specific gravity of the gas is 0.55 to 0.57 for dry gas, and 0.60 to 0.68 for wet gas. The specific gravity of crude oil is 0.75 to 0.79 for condensate (colorless and transparent) and 0.80 for black crude oil from the oil reservoir. Gas oil ratio is 8,500 to 3,000Sm3/kl STO for condensate reservoir and decrease inversely with depth. It is ca, 450 Sm3/kl STO for the oil reservoir.

2-6

'-._/

@t


2.4 Production System for NANG (1) Well Exploratory drilling for NANGwas conducted at the NK-l and NK-2 wells in 1961 and the NK-3 well in 1963in the Central district, and at the NK-13well in 1965in the North district. Based on the result of the exploratory drilling, production well drilling was carried out at a spacing of 700m to 800m. There are 22 installed production bases(including 8 abandoned bases), 44 wells(including 15 abandoned wells) and 51 production tubing (including 21 abandoned) up to the present (except the Shiunji distinct). At the beginning single completionwas generally used, wherein a mechanical packer is set inside 5-112inch casing with 2-3/8inchtubing. Multiple completion was tried only in wells NK-18,19and 23 and 24 in 1966 using dual string 2 zone completion.Thereafter, techniques and completion equipment of this Otis and Baker, was introduced in 1973and triple string, 3zone completionwas tried in with NK-40,41and 42, dual string, 3 zone completionin wells NK-43and 44 and single string, 4 zone completionin well NK-2 (workoverwell). As a result single string, multi-zone completion using Otis's completion equipment was generally adopted in this gas field as the more profitable form of multi zone completion. Multi zone completionwas applied to 9 wells; 5 single string completionwells, 3 dual string completion wells and I triple string completionwell. Subsequent immers'ion of water into the wells due to the water influx led to work over and/or abandon operations so that at present only 4 single string and 1 dual string multi zone completion wells remain in operation (exceptfor the Shiunji district). The newest well for NANGis the NK-66 which was drilled in 2012. In response to the geologicalstudy and reservoir simulation study in 2009 to 2011,the horizontal well was applied to this well and it was successful in increasing gas production. This well is still flagship production well. (2) Production method After the natural flow of NANGgas is controlled in production rate and reduced in pressure by a long nose choke at the well head (adjustable choke),it is transferred to the Central processing station through a gas gathering pipe line. After dehydration it becomeslift gas, injection gas or sales gas. As NANGis used as lift gas, the pressure of the gas gathering pipe line is about 3.1MPa (455.1psi) at the Central processing station. However, for wells which cannot produce at such a high pressure, the gathering pipe line pressure is reduced to 0.7MPa (99.6psi)at the Central 2-7


processing station.

(3) Production status The injection gas rate and production rate of NANG is controlled in accordance with user consumption. Production rate is controlled by opening and closing the well or by adjusting the opening of the bean under remote control from the central control room which is located on the Central processing station.

2.5 Production Facilities for NANG (1) NANG Base In the Nakajo gas field, there are 7 NANG bases in the North district and 7 in the Central district. At each base, there are 1 to 5 wells, long nose chokes to adjust production rate and indirect heaters to prevent hydrate formation.

>-

Christmas tree (Fig. 2.5-1) A Christmas tree consists of a well-head master valve, (No.1 master valve, No.2

master valve) an emergency closing valve, a cross, a pressure gauge, a safety bean, a bean nipple and so on, and is usually called a "Christmas tree" because of its appearance. Normally 2 pressure rating types are used; API 10,000 psi and 5,000 psi ratings.

Fig. 2.5-1 Christmas tree of NANG well

>-

Indirect heater (IDH) 1 or 2 indirect heaters are installed in each base to prevent the gas temperature

failing below the hydrate generating temperature

2-8

due to adiabatic expansion via

0X JX Nippon Oil & Gas

xploration

the choke or a reduction in outdoor temperature. The heater is of the water bath type, having a capacity of 0.2 to 1 million BTU. The heater has a pilot burner and a main burner and the temperature is controlled .by the burner control. There are two control types, i.e. field control and remote control. (2) Central Processing Station (Fig. 2.5-2) Natural gas gathered through the pipe line from NANG wells to the Central processing station initially enters into a high-pressure 3-phase separator where it is separated into gas, oil and water on the basis ofthe differencesoftheir specificgravities. Th_~pefore, the separated gas, oil and water are processed as,follows.

Fig. 2.5-2 Central Processing Station ~

Gas treatment After separation, the gas still includes oil and water, the amount depending on

the temperature (18°Cto 30°C)and pressure (3.1MPa (455.1psi» of the separator. Therefore, if the temperature drops after the separator outlet, this oil and water is likely to condense in the pipe line and can be the source of the followingtroubles. a) The oil retained in the pipe line cannot be collected,leading to economiclosses as well as possibly causing trouble for gas users. b) Water produces corrosion and generates hydrates in the pipe line to the point where it can plug the pipe and prevent gas flow. For the above reasons, the gas is further dehydrated to extract the water. The dehydrated gas is supplied to NGDWbases as a lift gas for NGDWwells and to gas 2-9


users as a gas for sales after being mixed with NGDW in a blending tank via a receiver tank. The gas is partly supplied to injection gas compressoras an injection gas.

)i;>

Crude oil treatment As the crude oil contains a large amount of light components such as gasoline

etc., as well a great quantity of dissolvedgases such as methane and ethene etc,.the .vapor pressure of crude oil is high, even after being held in a storage tank, making it still dangerous to transport it in this state in a tank lorry. Therefore, the crude oil is stored in stock tanks just after being stabilized by separating methane, ethane and propane in the crude oil stabilizer.

)i;>

Water (fromNANGwell) treatment Natural gas is dissolved in water corresponding to separator pressure (3.1MPa

(455.1psi) in this case). Therefore, dissolved gas is released by introducing this water into a low pressure separator (0.2MPa (28.4psi», and it is introduced into the suction ofthe compressor at the North processing station. Since a large quantity of water trapped in the pipe line is discharged toward the separator at one time, it is received in a holding tank and then injected under pressure into the ground at a constant rate. The main facilities used in these treatments are as follows.

)i;>

High-pressure 3-phase separator (Fig.2.5-3and Fig.2.5-4» It separates the gas, oil and water, with the gas being removed from the top, the

oil from the middle and the water from the bottom. The oil water interface is e

controlled at a constant level by a pneumatic level controller and control valve, the oil being supplied to a crude oil stabilizer and the water to a low-pressure separator. Further, the separator pressure is maintained at a constant pressure by control valve at the downtime of the separator.

2-10

'-..../

~


Fig 2.5-3 3 Phase Separators in Central Processing Station

To refrigerating hydration unit

Frqrn well

-----~

Well water Injected into ground after gas removal

Fig 2.5-4 Schematic of 3 Phase Separators

~

Flon type refrigerating

dehydration unit (Fig.2.5-5 and Fig.2.5-6)

In this unit, oil and water are separated from the gas out of the high-pressure 3-phase separator by condensing oil and water vapor after the gas temperature has been reduced. Flon is used as a refrigerant and the unit is composed of a Flon gas compressor, temperature

an air cooling Flon gas condenser, a gas cooler and a low

separator.

Oil and water vapor condenses while the gas is cooled in the gas cooler. Water is separated

from oil in the low temperature

separator by being absorbed into

glycol. After Flon gas vaporized in the gas cooler has been pressurized by compressor, it is re-Iiquefied in the cooler and supplied to the gas cooler again. Gas cooling

2-11


temperature

is automatically controlled by Flon level and compressor load.

Dehydrated gas is then supplied to NGDW wells as a lift gas and enters the gas transfer line to users through a receiver tank. Some gas is also supplied to injection gas compressor as an injection gas.

Fig. 2.5-5 Flon type refrigerating dehydration unit

SOK Separator

------~

40K Header ~------__.

~.-.---.--.......

on

·· ·

J;1,

Q1

(Ev~;"+€>

··~:;J~L··Ckl ..I.

.i····..·..·..

i

i :

_ • __u

u .. ~.(

.1

Receiver )

.. , u.

"

. .

Natural gas Flon gas Flon liquid

Condenser

Fig. 2-.5-6Schematic of Flon type refrigerating dehydration unit

)i>

Crude oil stabilizer (Fig. 2.5-7 and Fig. 2.5-8) This is a crude oil vapor pressure adjusting unit consisting of an oil receiver, a medium pressure separator, a heat exchanger, a fractionating tower and heater.

2-12

JX Nippon Oil & Gas·Exploration

The crude oil coming out of the separator is fed to the oil receiver and then to a medium pressure separator at a constant rate. Dissolved gas is extracted from the crude oil by pressure deduction in the oil receiver (O.8MPa(113.8psi» and medium pressure separator (O.6MPa'(Sfi.Spsij). Crude oil from the medil~~:pr~:ure separator enters into the tower (O.03MPa (4.3psi» after being heated, while gas is separated from oil by effectivegas-liquid contact in the tower. After a part of the heavy content is recovered from the gas by being cooledin the heat exchanger, the gas is transferred as a.tail gas to the North processing station and pressurized by gas transfer compressor. The crude oil is, on the other hand, transferred to the crude oil tank. As it is necessary to keep the tower bottom temperature constant in order to stabilize vapor pressure, the temperature of the heater is maintained at the' appropriate level.

Fig. 2.5-7 Crude oil stabilizer

2-13


5Oi
Oil feed, Oil fE*ld To oil tank Oil reflux

MedilXll pressure gas '(6-8KSC) U::M pressure gas (O.3KSC)

.' Heater

I

LTS

Oil transfer .PlJllP

tI I

i

.'IV SOOk! tank:

North processing s-tation

Fig. 2.5-8 Schematics of Crude oil stabilizer

);;>

Receivertank (Fig. 2.5-9) Response to rapid fluctuations in user consumption is made by adjusting the

production rate of the NANGwell and the injectiongas rate. However, as it is difficult to respond completely to small fluctuations in consumption and, because it takes time from adjustment of the production rate to the appearance of the control result, a receiver tank is installed to absorb the differencebetween consumption and production so that fluctuation in the pressure of gas transferred to users can be prevented. That is, if the user's consumption rate is greater than the production rate, the 2-14

JX .Nippon Oil & Gas Exploration

receiver tank pressure decreases and if smaller, the pressure increases. A computer and/or an operator control the production rate or gas injection rate while surveying the balance so that the receiver tank pressure is kept within a predetermined range. ~

Blending tank (Fig. 2.5-9) Gas compositionand heating value of NGbW, NANGand the crude oil stabilizer

off-gasesvary widely. Therefore, a blending tank mixes these gases to provide a homogeneous gas for subsequent use or sale.

Fig. 2.5-9Receivingand Blending Tanks ~

Gas injection compressor (Fig. 2.5-10) This is a horizontal 2-stage balanced compressor,which smoothies out.the rapid

fluctuations in production rate. It has an injection capacity of 100,800 Sm3/D at an output of 260 kW. The compressor induces a part of user supply gas of 0.6MPa (87.0psi)pressurizes it up to about 2.5MPa (362.6psi) after the 1st stage, then pressurizes it further up to 8.1MPa (1174.8psi) after it is intercooled to improve the compression efficiencyat the 2ndstage before supplying it to the injection well. In order to control the injection rate, load can be selected from 0%, 50%, 75%, 100%by unloader system and can be changed by remote operation.

2-15


Fig. 2.5-10Gas injection compressor

);;>

Crude oil stock tank (Fig. 2.5-11) Two cone roof tanks with a capacity of 500 kl and 1,000 kl respectively are

installed to store crude oil supplied by pump from the crude oil stabilizer.

Fig. 2.5-11Crude oil stock tank

);;>

Crude oil loading facility (Fig. 2.5-12) Crude oil produced in this gas' field is loaded by tank lorry or tank' car. In the

same yard, a tank lorry loading facility is installed and crude oil is loaded from the crude oil tank to the tank lorry by loading pump, volume is metered by volumetric flowmeter. On the other hand, when using tank cars, crude oil is transferred by central transfer pump to the tank car loading yard located 8 km from the central yard and 2-16


then loaded to the tank car.

Fig. 2.5-12Crude Oil Loading Facility (3) Pipe L~ne(Fig. 2.5-13) Natural gas produced in this gas field is delivered to users through a pipe line. The structure and function of pipe line are as follows.

>-

NGDWgathering line In this line, separated gas is transferred from the open separator at the NGDW

base to the North or South processing station by compressor suction. As oxygenis likely to be induced through pin holes in the pipe, thereby possibly creating a dangerous situation and therefore, the oxygen contentin the gas is monitored at the North and South processingstations. Water draining facilities are also installed at 10 places in the North district and 11 places in the South district since water is condensed in the pipe due to the reduction in gas temperature. Diameter of the pipe is 10 to 24 inches and pressure is usually -100 to +200 mmH20.

>-

NGDW transfer line . This line transfers pressurized gas from the North and South processmg

stations to the Central processingstation. Pipe diameter is 10 to 12inches and line pressure is about 0.6MPa (85.3psi).

2-17


);>

NANGgathering line This line transfers natural flow NANG to the Central processmg station.

Untreated gas flowin the pipe so that when the line temperature falls in winter, the pipe line is likely to be plugged by hydrate. Therefore, in the North district, the pipe line is heated by means of line heaters (L.R.) installed at 3 places to ensure that gas temperature does not fall; below the hydrate generating temperature. Line heaters of the bath type, similar to indirect heaters, with a capacity of 0.5 to 2.5 million BTU are used. They are controlled in the same way as indirect heaters. At present there are three 3 inch lines in the Central district, two 4 inch line and one 3 inch line in the North district.

);>

Lift gas line This line supplies lift gas to NGDW wells. It transfers NANG treated at the

Central processing station, or NGDWpressurized by 100 kW lift gas each NGDW base at a pressure of about 3MPa (440.9psi). Pipe diameter is 4 inch the main line and 2 or 3 inches in branch line. );>

User supply gas line Natural gas is supplied at present to Kyowa Gas Chemical Industry, Mizusawa

Gas Chemical Industry and Nakajo Municipal Gas through the 12 inch main route line. In addition, there is route 1 (4 inch) to KyowaGas Chemical Ind. And rout 2(4 and 6 inches) to Nakajo Municipal Gas. The crude oil line for tank car loading runs along the 4 inch line to KyowaGas Chemical Industry.

2-18

JX Nippon Oil & GasExploration

87 psi (O.6MPa)

r::=:=:=:::>

NANG Wells Low WHP

~------------------------------~

I

NANGgathering line

HighWHP

435 psi (3.0MPa)

CPS

87 psi (O.6MPa) •

tr;::::;===========f.---i-... ----

... User

User supply ga line

Gas Injector

NGDWtransfer line Compressor

Fig. 2.5-13 Gas distribution system in Nakajo Field

'-

2-19

@lX

JX Nippon Oil 8, Gas Exploration

Chapter 3: The Characteristics of Natural Gas Dissolved in Water (NGDW) Stratigraphic Successions

3.1

Please refer to 2.1 Stratigraphic

Successions.

GeologicalStructure

3.2

Please refer to 2.2 Geological Structure

NGDW(Natural Gas Dissolvedin Water) Reservoir

3.3

The NGDW reservoir stretching

south-north

is distributed

in a syncline west of the Tsuiji Anticline

and forming the reservoir rock of sandy conglomerates

and

sandstone in the Haizume and Nishiyama formations. These reservoir rocks have a tendency to thin out gradually towards the Tsuiji Anticline from the NGDW reservoir. The gas reservoir is distributed throughout a depth from 200m to 1,700m and is divided into 11 reservoirs ranging from zone 5 to zone 15. As a number of useful elements are contained in the "interstitial dissolves the NGDW, "interstitial

water", which

water" is gathered in the field as a source material,

especially for iodide recovery. This NGDW is also characterized

by a very high level of

C02. The thickness of each gas reservoir is about 30 to 70m. Porosity is 20 to 30% and gas/water ratio is 1.0 to 1.7(Sm3/k1).

3.4 Production System for NGDW (1) Well After success with the exploratory drilling of the R-l well, development of the NGDW field was carried out and bases N20 to N26(South district) were installed at a spacing of 300m along the coast line as a production base. 2 to 7 wells were drilled at each base and a well was completed for each gas reservoir. The perforated pipe completion method is used, wherein perforated pipe, connected to 8-5/8"casing is set into the well and cementing is applied around the casing above the perforated pipe.

(2) Production method Although the NGDW wells produced naturally

at the beginning,

th

pressure

decreased as production progressed, so that the method was changed to a gas lift and

3-1


recently ESP (Electric Submersible Pump) has been adopted to the new 3 wells. Gas lift production is a method in which high pressure gas is injected through a lift pipe into the well and interstitial water (specific gravity = 1.0) is lifted up due to reduced apparent specific gravity. For this purpose, a 1 inch lift pipe is set into the casing and lift gas (NANGis utilized for the lift gas, but if there is a shortage of NANG supply,gas is pressurized by a 100-kwgas compressor)is injected. ESP is an artificial lift which consists of downhole centrifugal pumps, an electrical motor which transforms the electrical power into kinetic energy to turn the pump, a separator or protector to prevent produced fluids from entering the electrical motor, and an electric power cable that connects the motor to the surface control panel. In 2014, ESP has been introduced for the first time in this field. Currently the effect is being monitored. After being lifted up to the surface, the natural gas interstitial water are separated in an open separator. Natural gas is induced and pressurized by 200kw gas transfer compressors at the North and South processing stations and transferred to the Central processing station after dehydration. (3) Production status As NGDWis produced by the gas lift method, production rate is usually constant. Therefore the rate is determined on the basis of the minimum requirement of a minimum consumption time-band. Consequently,the normal production rate of 11 or 12 wells is about 21,000 Sm31D gas and 13,000kllD interstitial waters and the required lift gas amount to 50,000 Sm3/D.

3.5 Production Facilities for NGDW (1) NGDWbase NGDWbase are installed at a spacing of 300m along the coast and there is a total of 15 bases consisting of R-1, N10-16 (North district) and N20-26 (South district). At each base there are 2-7 wells. Interstitial wateI)and natural gas are separated in an open separator in this base. The separated gas is induced by compressors at each North and South processing station and the degassed interstitial water is transferred to Iodine production plant. The facilities installed at each NGDWbase are described in detail in the following. ~

Well (Fig. 3.5-1) 3-2


As described in chapter 3.4, NGDWis produced by the gas lift method. Therefore, III

NGDW wells, a

i' inch

lift pi~ is installed inside an 8 inch casing and the

interstitial water is lifted up through the outside of the lift pipe by injecting lift gas which is produced from the well-head to the open separator through a steel or FRP pipe. ____. Lift

gas

____.

0

0 0

Lift

To separator

g"8S

0 0

0

0

0

0

I" ll! t pipe

0

0 0

I

_)/ I

I

~1

Re e e r vo I r

Fig. 3.5-1Wellfor NGDWwith gas lift ~

Open separator (Fig. 3.5-2) In this type an open bottomed container is put down into a water tank. The mixed

flow of natural gas and interstitial water from the well-head enters the separator through a pipe installed at the center of the separator and the gas separated and interstitial water by the differences in their specific gravities. The bottom of the separator is always filled with interstitial water in order to seal. Natural gall to North or South proees$ln& station

~

--

Interstitial water

Fig. 3.5-2 Open separator

3-3


);>

Chemical injection pump (Fig. 3.5-3) As, in the NGDWwells, scale deposits gradually build up on the inner surface of

the casing with the continued flow of interstitial water and will eventually plug the casing and make production impossible. In order to prevent such a build-up of scale an anti-scale agent (condensedphosphate) is injected into the lift pipe of each well by chemical injection plunger pump at each base. Pump suction is connected directly to a chemical line from each South and North processing station.

Fig. 3.5-3 Chemical injection pump (2) North Processing Station As the pressure of gas separated

III

the separator at each NGDW base nears

atmospheric pressure, it cannot enter directly into the gas transfer line which has a pressure of about 0.6MPa (85.3psi). Therefore, 200 kW gas transfer compressors are installed for pressurizing at each North and South processing station. Gas from wells R-l and NIO-N16is gathered to the North processing station and gas from wells N20-N26 to the South processing station. As the pressure of the gas in the gathering line is controlled to within a range of -100 to +200 mmH20, it sometimes reaches a vacuum. Consequently,if there are any pin holes in the piping of gas gathering line system at this time, air is induced into the piping, creating the possibility of an explosion. Therefore the 02 percentage in the gas is always analyzed, and when it is over 0.3%,the gas transfer compressoris stopped by a sequence of emergency stops. After the gas gathered to each North and South processing station is cooledby direct cooler,it is pressurized by a gas transfer compressor and fed into the gas transfer line after dehydration. 3-4


The facilities installed at the North processing station are described in detail as follows. _);;>

Direct cooler (Fig. 3.5-4) The gas temperature is reduced by direct contact with sprayed coolingwater as the gas rises through the shower.The object of reducing gas temperature is as follows: • o

The conde~sed water in the gas gathering pipeline sometimes causes damage to the compressor; therefore, the condensed water should be removed before the gas is induced by compressor.

•

Gas volume can be reduced by lowering the temperature, thereby improving compressor efficiency.

•

Water content can also by lowered by reducing the gas temperature so that the succeeding processes become easier.

. o0

Fig. 3.5-4Direct cooler

_);;>

,Q )

200-kw gas transfer compressor (Fig. 3.5-5) The horizontal two-stage balanced compressor has capacity of about 50,000 Sm3/D. It consists of two cylinders, as intercooler and an aftercooler. The intercooler improves the efficiencyof the second stage by coolingthe compressed gas after the first stage, while the aftercooler cools the compressed gas about gOoe after the second stage by up to 15°e to 20 e and, as a result, water vapor 0

is condensed and removed. This 2-stage compressor pressurizes gas from atmospheric pressure to about O.lMPa (21.3psi) in the first stage and to about 0.6MPa (88.2psi) in the second stage. At present 2 compressors are installed at the North processing station, one of them being a spare for emergencies. 3-5


Fig. 3.5-5 200-kwgas transfer compressor ~

Glycoldehydrator (Fig. 3.5-6) A glycoldehydrator is installed to further remove water from the gas coming out ot the compressor after cooler.Glycolis injected at the avsorber top to absorb moisture in the gas coming-downand is drawn out at the bottom. Glycolcontaining absorbed water is transferred to a glycolreboiler, where it is heated up to 180't to 200 C before being returned to the original state after D

releasing its water (this process is called "regeneration").The regenerated glycol is supplied again to the absorber by motor-driven pump. In this dehydrator triethylene-glycolis used as an absorbent. On the other hand, the gas flowsfrom the absorber to the gas transfer line after glycoldehydration. The dew point of such dehydrated gas is about -7°C.

Fig. 3.5-6Glycoldehydrator );;>

Anti-scale agent supply unit (Fig. 3.5-7) 3-6


The anti-scale agent for the North district NGDWis prepared in a batch at the North processing station and supplied by motor-driven pump to each base where is mixed with water to the correct concentration. When the line pressure drops, the supply pump is automatically engaged and the agent is supplied to each base.

Fig. 3.5-7Anti-scale agent supply unit (3) South Processing Station The facilities installed at the South processing station are basically the same as at the North processing station (4) Central Processing Station ~

100-kWlift gas compressor (Fig. 3.5-8) This is a horizontal one-stage balanced compressor with a capacity of about 34,000 m31D. Although lift gas for NGDW wells is usually dehydrated NANG from the Central processing station, it can also be obtained by pressurizing the gas from the NGDWline (about 0.6MPa (88.2psi» up to about 3MPa (440.9psi)by 100-kW lift gas compressor. However,when NGDWis pressurized, it is likely to produce a hydrate because the pressure dew point of gas is high, so that a glycol dehydrator is also installed, even for 100-kWlift compressor.

3-7


Fig. 3.5-8 100-kWlift gas compressor

)0>-

Amine gas treating unit (Fig.3.5-9) This is a' gas sweetening unit consisted of inlet scrubber, amine contactor, amine flash tank, amine cooler, amine still, amine reboiler etc. . The amine contactor is a trayed tower, 20 Nutter valve trays and mist pad at the top. The lean amine enters the tower at the top and flowsdown, contacting with sour gas and removes the acid gas from the inlet sour gas. NGDW contents 5% of C02 and 10 ppm of H2S. Using this amine gas treating unit, C02 is removed to 0.5% and H2S is removed to less than 2 ppm.

Fig. 3.5-9Amine gas treating unit 3-8

0X JX Nippon

Oil & Gas Exploration

Chapter 4: The Characteristics of Shiunji Oil Field 4.1

Stratigraphic Successions Please refer to 2.1 Stratigraphic Successions.

4.2 GeologicalStructure Please refer to 2.2 GeologicalStructure

4.3 Shiunji Oil Reservoir From 1960s to 1970s, NANGform Tsuiji district was a main production of our field, while exploration activities were also performed to neighboring region to find another gas reservoir. In 1978, not gas but oil reservoir was found in the Shii a formation of Shiunji district by exploration well of NK-53, and then production test was succeeded. The oil from Shiunji district is not condensate but medium crude oil with 0.83 of specific I

gravity. An oil processing station was newly built in Shiunji district for the process, storage and unloading of produced crude oil.

4.4 Production System for Shiunji Oil Field (1) Well (Fig. 4.4-1) In the Shiunji district, there are 5 installed production bases and-g.wells (including 4 abandoned wells) was drilled from basis. Due to the low productivity of the oil reservoir, it was difficult to achieve stable production. However,some wells including NK-53 were re-completed to horizontal well and achieved to gain the productivity. ~_wells are currently producing and the new drilling project was in the planning stage.

Fig4.4-1 Oil well (NK-53)at Shiunji District 4-1


(2)Production method Produihon method is natural flow.After the natural flow of ~il and associated gas are controlled in production rate and reduced in pressure by a long nose choke at the well head (adjustable choke), they are transferred to the oil processing station in Shiunji district. In the oil processing station, processed oil was storage in oil tank and directly shipped by tank lorry, while the processed associated gas .is transferred to central processing station and blended with gas from NANGand NGDW.

·4.5

Production Facilities for Shiunji Oil Field

(1) Shiunji Oil Field Base In the Shiunji Oil Field, there are 5 bases in the Shiunji district. At each base, there ,.ar.e 1 to 4 wells, long nose chokes to adjust production ,,'ate and indirect heaters to prevent hydrate formation were installed to each bases as well as NANGbases. Due to the proximity of oil processingstation and also lowpressure, line heater is not installed. If there is a possibility of the hydrate formation, methanol was injected to prevent it. (2) Oil Processing Station 2 indirect heaters are installed in oil processing station to prevent the gas temperature falling belowthe hydrate generating temperature. Produced fluid gathered through the pipe line from each Shiunji oil field base to the oil processing station initially enters into the indirect heater and heated to 50°C, and then enters into high-pressure 3-phase separator where it is separated into gas, oil and water on the basis ofthe differencesoftheir specificgravities. Separated gas enters into the pipe line to North Processing Station and blended with NGDW,after that processedwith NGDW. Separated oil enters to the secondheater and heated to 60°C,then the light components was separated and enters the second 3 phase separator. And the separated oil enters in the storage tank. There are two oil storage tank of 295kl. The oil was shipped by tank lorry with oil loading unit. Separated gas from the 2nd separator enters flon type refrigerating dehydration unit and the gas is used as supply gas for the fuel of heaters.

4-2


3 Phase Separator

Crude Oil Loading Station

Figure 4.2 Facilities on Oil Processing Station for Shiunji Oil Field

4-3


Chapter 5 : Instrumentation Network Asdescribed in Chapter 1, the Nakajo gas field consists of the NANG wells, the Central processing station which is the processing facility for NANG,the NGDWwells, and the North and South processing stations which are the processing facilities for NGDW. In addition to these facilities, in the Central processing station monitoring room, all of the facilities, including the pipelines that connect the supply destination points, are monitored and controlled in an integrated setup. This monitoring and control system is comprised of the comprehensive instrumentation control computer system (CENTUM) that is installed in the Central processing station along with the telemeters and the communications network that supports this system.

5.1

Comprehensive.Instrumentation and Control Computer System (CE~TUM) CENTUM, which forms the core of the instrumentation network of the Nakajo gas field, was

introduced in December of 1984 as CENTUM-Vfirst. And CENTUMCS1000was replaced in 2000 second, and then CENTUM CS3000was again done in 2010 last. The CENTUM system was designed with the aim of ultimately providing "panel-free" instrumentation, and total redundancy provided for all important components. Provisions have been taken so that in the unlikely event of any trouble, the system will not go down and will be able to continue operation.

The main system consists of the follows; (1) Field control station (2) Operator's station

In 2015, the existing CENTUM CS3000 will be replaced with the new CE TUM VP. The hardware and the diagram of the monitoring and control network for CENTUMVP are shown in Fig.5.1-I.

5-1


f

:f(~

~.e. t!:!"Q) .g~ ~

I2SI

:!l

*Q • I "... $ 0

Z

z

111

"\';:: _= _-. c; 'I

I ro ~

i

~

~~ I ~I

.,..,.1-,

0

z

1r1 ~~ S.. 5~

~

0(

~

~ I

o

.. ~ -

_.

.

Z I o ~I

Z

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JX Nippon

on. Gas Exploration

5.2 Telemeter Systems Among the input signals that are input to CENTUM, a large proportion are electric current signals and set point signals that are sent directly via telecommunication (telephone, optical fiber, etc.) cables.

The main telemeter systems consist of the follows; (1) North processing station telemeter

..

(2) South processing station telemeter (3)Users telemeter (4) Optical fiber telecommunications telemeters for NGDWwellpads

5.3 TelecommunicationsCable Network The signalsthat carry out the monitoring and control tasks in the central monitoring room are all transmitted via dedicated telecommunications cables. The telecommunications cables are

.. .

,

usually 5 to 75 paired anti-corrosion cables having a thickness of 0.9 mm dia. and 1.2 mm dia. Which of these is used is determined by the distance of transmission. With respect to the methods for installing these cables, both burying them underground and suspending them at a certain height are used, but the major portion is buried underground. In the case of burying them underground, subsidence beneath the surface of the earth

IS

prepared and the cable is laid by the snaking method.

5.4 Power Supply The instrumentation power supply in the Central processmg station is fully redundant. Ordinarily the supply of power is received from TohokuElectric Power co.,inc. (an electric utility). In preparation for the unlikely event of a failure such as a power stoppage, occurring, the following backup systems are provided.

(1) Uninterrupted power system (UPS)

This equipment is an uninterrupted power system that contains a built-in battery. During ordinary periods, the battery is kept fully charged so that when a power stoppage occurs, electric power can be instantaneously supplied from the battery. This provides assurance that the measurement instruments will never be stopped. Moreover, the capacity of this UPS is approximately 30 minutes at 10 kVA. 5-3


(2) Emergency generator (EACG) An emergency generator powered by a diesel engme having a capacity of 100 kVA is also available.

In the event of a power stoppage, this

generator

is automatically

activated

in

approximately 40 seconds. For long power stoppages, this generator not only assure the instrumentation

power supply, it

also provides power to the power supply unit in the Central processing station (with the exception of the gas injection compressor) and the lights. After recovery from a power stoppage, the power supply is automatically switched back from the generator to the regular power supply system and the generator is turned off. When this switch back is made, another instantaneous

power stoppage occurs and the power supply components are

halted: The UPS backup of the measuring instruments,

5-4

however, is not affected whatsoever.

<:>

@t


Chapter 6 : Measurement and Control Instruments 6.1 Measurement Instruments In general, the use of the word measurement instrument refers to a "machine that measures some object,"such as the quantitative measurement oflength, weight, temperature, time and so on. These measurement instruments are used for most frequently for measuring such things in particular as flowvolume, temperature, pressure, and level. These meters were used at first just as separate units and only to display the process status. Recently,however, they have become to be employedfor the measurement of "process variables" that are measured quantitatively and then are used as automatic control to automatically adjust the value so that it meets a target value. The meters in use at the Nakajo gas field can be broadly divided into two types, those that provide on-the-spotindications and those that provideindications to remote locations. The latter groups are basically those that are linked to CENTUM.The data that is measured by these meters is controlled in a variety of combinations. The principles and the applications of these meters as employedat this processing station are describedbelow.

(1)Temperature measurement device As methods to measure the temperature of equipment, both the method that utilizes changes of electrical resistance caused by temperature and thermal e.m.f well as the method that uses the expansion and contraction of materials are frequently used. Using the former method are temperature detecting resistance element thermometers and thermocouple-typethermometers. Using the latter method are pressure gauge type thermometers and liquid-filled thermometers. The temperature measurement devices that are in use at the Nakajo gas field are described below.

1) Temperature detecting resistance thermometers

The electric resistance value of metals changes according to changes in temperature. By utilizing these characteristics, a temperature detecting element that can measure the temperature is available and it is suitable for measurements in the range of 50°C to 200°C. Platinum is used for reasons oflinearity and the measurement range. 6-1

@c

JX Nippon Oil & Ga.s Exploration

In order to use this principle for the measurement of temperatures, in addition to supplying an electrical current to the resistance element, it is also necessary to combinethis with a converter for measurement of the resistance value. This combination is then installed in an instrumentation room that is closeto the measurement point. In this gas field, all temperature data that is sent to the Central processingstation, including that for remote automatic control,is detected by the temperature resistance detecting element.

2) Liquid filled thermometers (Fig.6.1-1)

CapL_1a_ry Ai

;d:Jt¥;;'~h¥!,' ;.

"'L'~

~

Sca_e

Fig. 6.1-1Liquid thermometer

The most common type of thermometer is the so-called "bar" thermometer. This is a bar-shaped device in which liquid is sealed in a glass-tube and the temperature caused by heat-induced expansionis indicated by the length of the liquid column. As the liquid used for filling the tube, mercury, alcohol,and other materials are used. This type of thermometer is employed for measuring the atmospheric temperatures, vessel temperatures, there is the method that employs a thermo-well which is attached to the measurement point and the thermometer is inserted into this. The method that securing the thermometer on the vessel or pipeline surface using putty is also available. This is a simple and low-costthermometer that is widelyused for on-the-spotindication ofthe temperature.

3) Pressure gauge type thermometers (Fig.6.1-2) This may be called a Bourdon tube thermometer and is available in three utilizing either liquid expansion, gas expansion, or vapor expansion. In the case of using liquid expansion, the 6-2

/

@c

JX Nippon Oil " Gas Exploration

expansion of sealed liquid is converted into the movement of a needle through a Bourdon tube. Mercury is used for the sealed liquid. This type of thermometer is used for the measurement of heater temperatures, pipeline temperatures,

and

separator

temperatures.

The

measurement

location and

taking

measurements by inserting the thermometer into the thermo-well. This type of thermometer is in wide use for on-the-spot indication of temperatures.

Dial

Bourdon-tube

Temperature sensing

Fig. 6.1-2Pressure type thermometer

(2)Pressure gauges Pressure gauges can be viewed according to the measurement range and broadly divided into gauges: Vacuumgauges and compoundgauges. Gauge pressure (MPa)is generally used y these meters, but types that employ ./

For the purpose of measuring pressure, a force called pressure is used and a solid object is moved;methods which use conversioninto a shape that can be seen by the eye or conversioninto an electrical signal are both utilized. Currently, for pressure data that is transmitted to the Central processing station, the pressure. is converted into an electrical signal by a force balance or an electrostatic capacity type pressure transmitter. For indication on site, a Bourdon type or liquid-filledtube pressure gauge is used.

1) Force balance type pressure transmitter For pressure transmitters, changes in pressure are detected as displacements in the position of the diaphragm. With this type of transmitter, a fixed disk is movedby the diaphragm and the interval from the differential transformer is converted. By effecting a current change on the secondary side of the differential transformer the 6-3

0c JX Nippon Oil & Gas Exploration

pressure is converted into an electrical signal.

2) Electrostatic capacity type pressure transmitter This type of pressure tra~smitter IS

(Fig.6.1-3)

operates by the displacement of a movable electrode which

fixed to the diaphragm caused by changes in pressure. Since the interval with the fixed

electrode changes, changes in the electrostatic capacity between the electrodes also appear and this phenomenon is used by this type. For pressure transmitters

used at the processing stations are all the electrostatic capacity

type. Power supply equipment (distributors) that read the transmitter supply in combination with these transmitters

output along with the power

is required.

Signal conditioner

Distributo!: (SHOO)

Transmitter

card (an)

CHl AC

p::JWer

SUW1y

+ -

4---20mA

24V DC 1--5V

Field

.... +

--------3IM:;----

Fig. 6.1-3 Instrumentation

DC

Inside converter-+· .• board in control room,

.'

Inside CENTUM cubicle

'

example of electrostatic capacity type pressure transmitter

3) Bourdon type pressure gauges (Fig.6.1-4) As meters that provide an on-site indication, these are the most widely used type of pressure gauges. By utilizing the expansion of the Bourdon tube according to pressure, the pressure is directly connected to an indication needle, thus enabling measurement of the pressure. This type uses a metal tube which is rounded so as to be close to a circular shape and has a cross-section that is elliptical in shape. The metal tube is manufactured from brass, phosphor 6-4

~


bronze, or stainless steel. For usage, it is necessary the materials of the Bourdon tube are selected according to the properties of the object being measured.

Fig. 6.1-4 Bourdon-tube gauge

At the Nakajo gas field, almost all ofthe pressure gauges are the Bourdon tube type.

4) Liquid pressure gauges (Fig.6.1-5)

A

B

.. I.. Fig. 6.1-5Liquid column manometer

With this type, the pressure can be directly'seen in the liquid-filled tube and both sides of U-shaped tube are filled by the liquid to an even level. When pressure is applied from one side, the differencein the height of the liquid in the two tubes can be determined. The liquids that are most frequently used are water and mercury. At the Nakajo gas field, this type of gauge is used for the measurement of pressure in NGDW gathering lines. In all cases, the liquid used in the gauge is water and these are gauges for the on-site indication of low pressures (kPa).

6-5

0t JX Nippon


(3) Flow-measurement

In the production and control of natural

gas and crude oil, measuring

the quantity

of the \

material is the matter of greatest importance. Flowmeters are one of the following two types: a.

Meters that measure the total volume of all of the liquid.

b. Meters that-measure

the velocity of the flow of the liquid.

Type 1 is represented by the rotator type meters, while Type 2 is represented by the orifice (differential pressure) flowmeters.

1) Rotary flow meters (Fig.6.1-6)

Fig. 6.1-6 Rotary displacernens meter

With this type of flow meter, the rotary flow meter is installed in the pipe and the fluid is passed through the space that is formed in the area between the rotor and the casing. This type measures

the flow volume from the volumetric capacity of the space and the

number of rotations.

In general this is used for measuring the volumetric capacity, but there are also types that can provide a reading of the instantaneous

value. Oval toothed gear types, Roots-types, and

rotary piston types are available. Although the accuracy of these meters is very high, when measuring the flow volume of a liquid, if gases are mixed with the liquid, an accurate value is not displayed. Moreover, unless a strainer

is installed

in the upstream

of the flow meter, foreign matter

cannot be removed,

thereby causing malfunction.

In the event of a malfunction, since the flow in the pipe is plugged, it is necessary to exercise precaution. 6-6

JX Nippon Oil ,. Gas Exploration

At the Nakajo gas field, these meters are used mainly for measurmg the flow of non-compressibleliquids such as crude oil and well water. In addition, these meters are also used for measuring gas at low pressure and/or in small amounts. Almost all of these are used as integrating meters that provide on-site readings. However,for flow measurement of the oil fed to the stabilizer, a pulse transmitter (1 pulse/l0 cc) is attached to the flow meter and this information (pulses) is sent to the Central processing station (Fig.6.1-7). S':'qr.a.l cxmditianer card (C'B )

Rotary" pistcn type fl~ter (Pulse

qeo.erator) -

,N2 p::Mer supply'

2502 1--5V

1 pllse/lOcc

Central Processing station side

Field side

Fig. 6.1-7Instrumentation example ofrotary piston type flowmeter (with pulse generator)

2) Orifice (differential pressure) flowmeters (Fig.6.1-8) If the fluid that is flowingin the pipe is restricted at some point, a change in pressure before and after that point will result. This change in the pressure is determined by the flowvelocityif the type of fluid, the specific gravity, and the size of the opening are constant. Therefore, differential flow meters use the method of determining the flowrate by measuring the pressure change from just before and after the opening. For the opening, an orifice is by far the most widely used. The structure of the orifice is illustrated in Fig.6.8.

6-7


Fig. 6.1-8 Construction of orifice(flange-tagtype)

An orificeis a disk that is 3 to 5 mm thick and has a precisely machined round hole in the center. The dimensions and the materials are selected according to the type, the temperature, the pressure, and the density of the fluid used in the operation. When measuring the flow rate by means of an orifice, a laminar flow at the point that the liquid passes through the orifice is required. For this reason, sufficient straight pipes must be installed in the upstream and downstream. Moreover,if the type, temperature, pressure, and density of the fluid change, the relationship between the differential pressure and the actual flowrate will be changed. It is therefore necessary to provide compensation when measuring under conditions such as these factors are changing. Although the accuracy of these meters is quite high, when the flowr~te is 10%or more below the measurement range, linearity with the differential pressure is lost and a large degree of error results. Although these restrictions exist, the equipment is quite simple and the accuracyis very high, so measurement of the flowrate by the orifice method is in fairly wide use. Particularly for the measurement of the flow rate of gas under high pressure, the simple construction of this equipment makes it far superior to any other method. At the Nakajo gas field, the gas flow rate that is measured and controlled in the Central processingstation is measured by these orificedifferential pressure flowmeters. Detection ofthe differential pressure depends on the pressure transmitters. Nonetheless, the principle is identical to that of pressure transmitters. 6-8


The change in the position of the diaphragm is converted into an electrical signal by the force balance method or the electrostatic capacity method for transmission. The differential pressure detected is read by CENTUM along with the data on pressure and the temperature at the measurement point. Temperature and pressure compensation are carried out within CENTUMand converted to flow data. For transmitting data to the processing station, the orifice plate has been designed so that a differential pressure of 25 kPa will be reached when the, maximum flow rate within the measurement range is flowing. As a result, when there are large changes in the measurement flow rate, changing the plate can be easily accomplishedat the location where the orificefitting is installed (Fig.6.1-9).

... Straightening

Downstream .

vane

Orifice fitting,

Fig. 6.1-9 Orificefitting

(4) Level meters

For level measurement of separators, towers and tanks, the followingmethods are commonly used: the method that allows the level to be directly observed (level gauge), the method in which a float is set afloat on the liquid surface and its movement up and downis transmitted to the outside (float type level meter), and the method in which the level is detected from the differential pressure between the upper and lower parts of a vessel (differential pressure type level meter).

1)Level gauge (Fig.6.1-1O) This is the most basic type of gauge for liquid level measurement and consists of a glass tube 6-9


for low pressure measurement and or a hardened glass tube for high pressure nieasurement that is surrounded by thick copper plates. When this type of level gauge is installed in a unit of equipment, it allows the liquid level to be directly observed. At the Nakajo gas field, all of the closed separators and tanks are equipped with level gauges.

Fig. 6.1-10Level gauge 2) Float type (Fig.6.1-11) The float is floated in the tank and its movement is transmitted to the outside by means of a wire. This arrangement causes an externally attached meter to rotate when the wire moves. At the Nakajo gas field, this type oflevel gauge is equipped in the crude oil tanks.

CD

® @

@

®

® ® Q)

®

Instrument Instrument support Special valve Guide-knob Tape Float Guide-wire Hook

®

Fig. 6.1-11Float type level gauge 6-10


3) Differential pressure level meter (Fig.6.1-12) When measuring the pressure inside a vessel in which the top part is filled with gas and the bottom filled with liquid, the pressure at the bottom is calculated by adding the product of the specific gravity and height of the liquid at the bottom to the pressure at the top. By this means, if the specific gravity of the liquid is constant, the height of the liquid level can be determined from the differential pressure between the top and the bottom, Currently the levels that are monitored and controlled in the Central processing station take measurements by this method. The differential pressure is transmitted

by the differential pressure transmitters

and the

set-up is the same as that used for the differential flow meters. The signal from the transmitter is multiplied by the specific gravity of the liquid within CENTUM and displayed as the height. The low-pressure side of the transmitter, for a pressurized vessel, contacts with the gas at the upper part of the vessel. Therefore, drain accumulated in the lead pipe on the low-pressure side may cause a level error. In order to prevent this error, the above lead pipe is sometimes filled with a sealing liquid beforehand.

130%

b!--t=::::lj::===========;::::::l:t:=l>¢==!

®

Low pressure

®

®

High pressure Seal-pot

~

Signal

® ®

Check plug

100%

® ®

Fig. 6.1-12 Differentialpressure 6-11

side

gate valve

side gate v Lv e

generator

Check. plug

High pressure Low pressure Zero

side drain valve side drain v lYe

adjustment

type level gauge

screw


(5) Other meters 1) Magnetic oxygen density meters As described in 3.5 (2) & (3), air should not be mixed in gathering pipe lines for NGDW, so that oxygen density is measured at the North and South processing stations, and for these measurements magnetic oxygen density meters are used. This meter employs the principle of operation that ordinary gases are diamagnetic substances, but on the contrary, oxygen is a magnetic substance. By attracting only oxygen to magnetism, other gases are allowed to flow through a different route. Resistance is placed on that flow route and is cooled by the flow of the oxygen. In other words, if the density of the oxygen is high, the temperature of the resistance will drop, while if the density is low, the temperature will rise. On the other hand, the size of the resistance value will change according to the temperature. Therefore, if this resistance can be measured, the oxygen density can be known. Currently meters of this type are installed in the North and South processing stations, and the oxygen density is monitored in the Central processing station.

2) Process gas chromatography The components of the gas that is flowing in a pipeline are continuously measured and this is referred to as gas chromatography. In gas chromatography, the sample gas and carrier gas are flowed through a column which contains fillers. Each of the components in the sample is analyzed by using the length of time required for it to flow through the column. The quantity of each component is measured by a thermal conduction system. In this system, the measuring filament is cooled by blowing the gas through it, and the temperature change of the filament is measured by the resistance value of the filament. From this measurement, the gas blown through the filament, that is, the quantity of each component, can be determined. The principles of this system are the same as that of the magnetic oxygen density meter. For this process gas chromatography, the sample line is connected to the pipeline and measurement of the samples is conducted for a fixed time interval. With this system, therefore, six different samples can be measured. Currently four different samples are being measured and this is used for controlling the 6-12

0t JX Nippon


operating conditions by checking the components of the sales gas, pre-processed NGDW gas, post-sweetened gas and consignment gas from JAPEX.

3) Switches for various alarms With respect to methods for monitoring the process status, one method gathers data by analog means and so that the status may be known at all times. Another method judges the status by whether or not a particular value is above or below a pre-set alarm point. For the latter

method, alarm

switches are used and digital signals are transmitted.

Regarding the principals involved, in either case, an electric circuit is opened or closed by a physical force, and sensing of the process conditions differs according to the measured object. For example, in the case of one method that is used, if the level is being measured and if a switch is moved by the motion of a float, Contact is made between two electrodes. For temperature,

the motion of a bimetal or Bourdon tube is used.

For flow or pressure, a pressure sensing device is moved by utilizing the force of the liquid itself. In addition to the above, a relay is activated by sensing the strength of a current flowing in an electric circuit, thereby transmitting

any abnormal condition in an electric motor.

6.2 Control Devices Regarding control devices, the device must have functions that actually enable it to change the process conditions so that the conditions of a given process match the desired target. In crude oil and natural pressure, temperature,

gas production facilities, these are used for the control of flow. rate,

and level.

In conducting process control, since it is assumed that the current conditions are necessary to be known, ordinarily a controller is used in combination with a measuring instrument. The difference between the set value and the target value is observed and as a result, an output signal is sent to the controller. In case it is acceptable to keep a process variable in the controlled object almost constant, no problem arises even if the variable is controlled by a field-mounted pneumatic controller. However, in case the set-point of the process variable must frequently be changed or high accuracy is required, field -mounted pneumatic controllers are not appropriate. For this need, where this type of control is required even at the Nakajo gas field, the process variables are sent to CENTUM by transmitters,

control calculations are performed, and the output 6-13


is sent to the control devices by electrical signals, thereby accomplishing the desired control. The principles and the applications of the control devices that are in use at the Nakajo gas field are described below.

(1) Control valves (Fig.6.2-1)

Pneum~t~c element

f~nal

control

Flange rating ASA 600 (R~ng joint type)

Fig. 6.2-1 Control valve (pneumatic)

With control valves, by changing valve opening, the volume of the fluid that is flowing the pipe can be controlled. Therefore, these valves are in wide use for controlling such variables as flow rate, pressure, temperature, and level. The control valve consist of a drive unit that opens or closes the valve according to a signal received fron{ a controller and the valve body that changes fluid volume adjusted by the drive unit. Drive units can be self-actuated, air-driven, electrically driven or use some other principle. The self-actuated -type used here at the Nakajo gas field are used to control pressure. Control is accomplished through maintaining a balance between the pressure and the strength of a spring. Although air for instrumentation

is not necessary, in changing the settings, the strength of the

spring must be changed while observing the downstream conditions, so it is somewhat troublesome. The air-driven drive units are the most commonly used . . 6-14

JX Nippon Oil "Gas Exploration

.'valve is moved via a piston that is directly linked to the diaphragm. Not only field mounted types but. CENTUM are used to drive control valves. For CENTUM pplication, an electro-pneumatic positioner is attached to the control valve. Electric signals from CENTUMare then converted to pneumatic pressure. Electrically driven control valves use an electric motor to adjust valve opening. Currently at the Nakajo gas field, these are used for the remote control of the production rate of wells. Motor-driven long-nose chokes, in the broad sense of the word, fall into this category.

!

(2) Electro-pneumatic positioners When the control valve is controlled from CENTUM,a device which receives an output signal of 4 to 20 rnA and converts the signal to a pneumatic signal to drive the diaphragm or to an electric signal to drive a motor is called an "electro-pneumaticpositioner" or "electro-electropositioner". The electro-pneumatic positioner compares the output signal from CENTUM with the valve opening and changes pneumatic pressure to be supplied to the diaphragm so that the opening matches the output signal (Fig.6.2-2). Clamp Unit:rrm Screw eMS)

Terminal box

I?ressuregauge (Supply air pressure) I Supply air connection PT--l/4 female

Bod.y

Pressure gauge (OUtput)

\ output connection PT-l/4

female

Fig. 6.2-2 Electro-pneumatic positioner

6-15

Screw (MS) Manifold


(3) Devices activated by digital output signals from CENTUM There are solenoid valves and motors. A solenoid valve is opened and closed by turning on and off a current flowing through its electromagnet. This type of valve is used for opening and closing the main burner of the heater, switching the supply air-gas system, opening and closing the shutdown valve of NANG wells, and operating the unloader of the gas injection compressor. For these operations, three-way solenoid valves are used for the shutdown valve and the unloader. On the other hand, a motor is started and stopped by turning on and off a current flowing through its circuit. This type of valve is used for starting and stopping the pump for tower level control of the stabilizer unit, and for emergency shutdown of the compressors in the North and South processing stations. These circuits are opened and closed via a relay that is operated when a digital output signal is received from CENTUM.

6-16

"-


Chapter 7 : Automatic Systems At the Nakajo gas field, the followingthree type tasks are assigned to computers to enable the integrated management and control of natural gas and crude oil production facilities.

Monitoring This task consists of constantly monitoring,the important process conditions in the operation and informing the operator by alarm when any abnormal conditions occur. There is approx.1600 monitoring points.

Controlling Automatic-control of the system so that the pressure in the pipeline is always kept constant even if external disturbances occurs. '

Preparation of the daily report An hourly report covering the items among the process conditions that should be stored (values for a one hour period) is kept in the computer and a daily report is printed each day. These tasks are performed in an integrated mannerby what is called an automatic system. The details of this system are described below. Moreover, to ensure that these tasks are performed smoothly,a Tag number is assigned to each point. The explanation belowwill be made with reference to these Tag numbers.

7.1 Monitoring At the Nakajo gas field, the monitoring of data at remote sites has a particularly important meaning. Where the point of monitoring is located for each station will be described below.

(1) North processing station The North processing station and the regional NGDWbases have particular monitoring points so that abnormal process conditions at them are judged by DCS of the North processing station. The important process points for the followingsare also monitored to manage the North processing station and the regional NGDWbases by DCS.


1) Gas production volume The gas productionvolumeis determined by measuring the volume oflift gas, the volumeof gas transferred, and the volume of gas sent to the Central processing station.

2) Gas gathering pipelines The pressure and the oxygen density in gas gathering lines is measured, and any abnormal conditions are sensed and notified.

3) Transfer gas pipeline The pressure in the transfer gas line is measured, and any abnormal conditions are sensed and notified.

4) 200kWgas transfer compressor The conditions of operating service, the load factor (50%,100%),and any failures (mild failures and serious failures) are transmitted by digital signals.

5)Anti-scalingagent transfer unit The amount of chemicals residue is monitored from the chemicals tank level; the chemicals injection rate is monitored from the descendinggradient ofthe tank liquid level; and also leakage is monitored from pressure decrease in the chemicals injection line, all of which are converted to digital signals to sense their abnormal conditions.

6) Peripheral devices The operating conditions of the coolingwater pump for the compressor,any failure conditions (mild failures and serious failures), the liquid level of the glycol dehydrator and the reboiler temperature as well as the level are transmitted by digital signals to sense their abnormal conditions.

7) NGDWbase No monitoring points are provided at the NGDWbases, but lift gas rate and pressure in the lift gas lines, pressure, oxygen density and transfer gas rate in the gas gathering pipe lines, and chemicals injection rate and pressure in the chemicals lines are monitored to judge the presence or absence of their abnormal conditions.

7-2


(2) South processing station Monitoring is conducted at the processmg station in the same manner as at the North processing station. In other words, the gas production volume in the South NGDW field is calculated, the difference between the total volume of NGDWproduction and the quantity of production in the North NGDW field is taken to be the quantity of production in the South NGDWfield.

(3) NANGbase 1) Wellhead pressure By measuring the well head pressure, the production capacity is monitored.

2) IDH (In-direct heater) water temperature By measuring the water temperature loss of the pilot burner flame (water temperature LO) is monitored.

3) Opening/closingwell SDV (Shut down valve) The opening/closingconditions of the well are judged by detecting the opening/closingsignals sent to the well SDV.

(4) Central processing station Since there are many monitoring points at the Central processing station, the various pieces of equipment are described below accordingto their classification. Furthermore, the devices that are used for control are described in detail in Chapter 7.2.

1) Separator For the No.1 thru No.4 separators, monitoring of the separators is performed by checking the pressure and the temperature, and at the same time preventing hydrate formation in advance.

2) Supply header The header and the line connected to it are monitored for any abnormalities by checking the pressure.

7-3


3) Freon type refrigerating dehydration unit A variety of data required for control can be measured (refer to Chapter 7.2 (5), (11». In addition to the above, compressor suction and discharge temperatures receiver

temperature

as well as Freon

are monitored to check whether or not any abnormality exists in the

unit.

4) Crude oil stabilizer In the crude oil stabilizer, oil receiver, reflux separator and stabilizer tower pressures as well as tower top and intermediate

temperatures

and oil receiver liquid level are monitored, all of

which are referred to when stabilizer control loop settings are made (refer to Chapter 7.2 (2) and (3».

5) Gas flow rate The production rate of NANG wells is determined from the flow rate, the injection gas rate, and the low-pressure production gas rate. Then the NGDW production rate is determined by subtracting the central lift gas rate from the total of the NGDW transfer gas rate and the central supply gas rate. In addition, in order to monitor the internal operating conditions, the gas rate in each line is measured. Moreover, to make appropriate temperature

compensation

for both pressure

and temperature,

the

and pressure are measured in the area of the flow rate measurement points. /

6) Gas injection compressors For the gas injection compressor, outlet temperatures inter-cooler and the after-cooler temperatures

and discharge pressures along with

and cooling water pressure are measured.

For gas injection wells, the injection gas rate, the pressure,

and the temperature

are

measured. Moreover, the casing pressure at the well and the external casing pressure are also measured.

7) lOO-kWlift gas compressor When the lift compressor is in operation, it is monitored by analog signals for the lift gas quantity, pressure, and temperature,

and by digital signals.

7-4


(8)Pipelines and supply destinations 1) NANGgathering pipelines For gathering lines, line pressures are measured at four points, thereby checking the line for blockage or leakage. Moreover,for line heaters installed at three locations, inlet -temperatures and outlet temperatures

are measured, thereby enabling the monitoring of the inlet

temperatures so that they do not fall belowthe point that would cause hydration. At the same time, these measurements make it possible to monitor the burner to make sure that loss of the flame does not occur.

2) Supply destinations

For the supply destinations, the gas flow rates received and the arrival pressures are measured, thus facilitating monitoring of the operating conditions of transfer gas pipelines and the supply destinations. Furthermore, with respect to the operator making adjustment to gas production volume, with there is a sudden change in the volume used at the supply destination, such adjustment is made before the effects of this change reach the receiver tank. For detail on the monitoring points of each NGDWpipeline, refer to the sections that describe (1)the North processing station.

7.2 Control (1) Feed control of the crude oil stabilizer (Fig.7.1) Separator PID control unit

Oil receiver

Reflux pressure separator Fig. 7.1 Crude oil feed control

7-5


The crude oil stabilizer conditionis stabilized easier if the constant amount of crude oil is fed. However,the feed rate of crude oil varies accordingto the production rate of NANG.Therefore, this crude oil is first retained in the oil receiver and then is fed always at the constant flow rate by means of a flowcontroller and a control valve installed at the receiver outlet line.

(2) Temperature control at the stabilizer tower bottom

The following two methods are available to control the temperature at the tower bottom (Fig.7.2). i) The crude oil is first fed into the tower, and then the oil rate through the heater is controlled to

control the tower bottom temperature. ii) The total quantity is first passed through the heater and then fed into the tower to control the bottom temperature by heater temperature.

7-6

<:>

JX Nippon Oil Ii Gas Exploration

Tower

r..··...... ···..._ ..··..······,j ~

TIC field unit

I ;i

~

I ;

,1 "

i

Supply 9

Fig. 7.2 Towerbottom temperature control of crude oil stabilizer

With method i), a control valve is installed in the line leading from the tower to the heater and the tower bottom temperature is taken as the input value and the PID controller sends an output signal to the control valve. In the case of method ii), on the other hand, there is no direct measurement of the temperature at the tower bottom, but heater temperature is kept constant through heater control described below.In this case, since setting of the heater temperature is done manually by the operator, it is necessary for the operator to constantly checkwhether the bottom temperature is appropriate. In comparison with method ii), this method does not involve directly observing the bottom

7-7


temperature, and the flowrate that is sent to the heater is fixed. Although this method has the disadvantage of its being very difficult to maintain a high temperature, it has superior stability at bottom temperature. Method ii), therefore, is usually used for operations at low temperature.

(3) Stabilizer tower liquid level control Currently, at the tower of the stabilizer, operations are carried out at a pressure that is closeto atmospheric pressure. It is, therefore, necessary to operate a pump to transfer the crude oil in the tower to the stock tank.

&

At the same time, it is necessary to keep the liquid level of the tower constant. For this reason, upper and lower limits are set for the level in advance, and when the level rises and exceedsthe upper limit, a pump begins to operate and transfers oil to the stock tank. The pump ceases to operate when the lower limit is exceeded,and by this means the liquid level is controlled,

(4) Temperature control for Freon type refrigerating dehydration unit (Fig.7.3) In order to dehydrate natural gas, the most important point is the temperature to which the gas IS

cooled by the gas cooler. The temperature is determined by the quantity of latent heat of

vaporization deprived when the gas is heat-exchanged with Freon (refrigerant) in the gas cooler. This quantity oflatent heat ofvaporization can be controlled by changing the level ofthe Freon and by changing the quantity that comesinto contact with the gas. For this reason, the coolingtemperature of the gas is controlled by a cascaded control system that actually combinestwo control systems in series, one for the outlet temperature of the gas and one for the level of the Freon. An output value is obtained through PID computation performed by detecting the deviation between the set-point and input value (Gas outlet temperature). This output value is used as the Freon level set-point, and the control valve is activated through output value calculation performed by detecting a deviation between the above set-point and input value (Freon level) Further, vaporized Freon gas is sucked and compressed by the compressor.As a result, it is necessary to change the load ofthe compressorto accommodatethe changes in the amount of Freon that is lost through vaporization. The compressorcapacitative control devicethat performs this operation is described below.

7-8

JX Nippon Oil "Gas Exploration

PIO Control

Unit

P"lon gas

1-

...

Gas (

··-...... ----· ·-i

Gascoole:r

_.

: .;:~:~~;~:.. ~.::~.:. .":

t

. Flon

l'quid

--------

~.... ,. ....

_

i

J .-----~_.__j

Fig. 7.3 Gas coolingtemperature control of Freon type refrigerating dehydrator unit

(5) Compressor capacitative control devicefor Freon type refrigerating dehydration unit, control of the number offans In the gas cooler,Freon that is in the form of a gas is compressed by the compressor and then cooledand liquefied by the condenser.The amount of Freon that .is lost through vaporization must be adjusted by switching the' capacity of the compressor, since such factors as the volume of gas production and the temperature of the outside air are constantly fluctuating. Since the pressure of the gas cooler is kept constant by using a pressure control valve, the suction pressure of the compressor on the downstream side of the valve rises when the amount lost through vaporization increases, and, similarly, falls when the amount lost through vaporization decreases. By this means, the capacitative control system for the compressor senses the suction pressure and raises the load when this pressure is high. It lowers the load when this pressure is low. The Freon that is compressed by the compressor,on the other hand, is cooledby the air-cooling condenser. However,since the Freon gas will not liquefy when there is insufficient cooling,the discharge pressure ofthe compressor rises. By regulating the number offans, which determine the amount of coolingperformed by the condenser,through checkingthis compressor discharge pressure, control with the optimum number of fans can be achieved. In addition to the above, when the discharge becomes excessivelyhigh, or when the gas cooler inlet temperature becomes excessivelylow,operation of the compressoris immediately shutdown. In addition, when a digital signal is receivedthat indicates that oil supply pressure is too low,the

7-9


same result takes place, e.g., operation is immediately shutdown.

(6) Heater temperature control This is by using the TIC field unit to control the heaters for the IDH unit, the LH (Line heater) unit, and stabilizer unit. The heater for the stabilizer unit is to control water temperature. However,for the IDH and LH units, emphasis is put on temperature control at a point where the gas passed through that heater enters the next heater. Also temperature upper and lower limits are preset, and if the temperature reaches the lower limit, the main burner is ignited by opening the TCV (Temperature control valve), while if it reaches the upper limit, the main burner is extinguished by closing the solenoidvalve. In this way, the heater for the stabilizer unit is controlled so as to keep the temperature constant and for the IDH and LH units, the gas temperature is controlled so that it does not become below the hydrate generation temperature.

(7) Sales gas control (Fig.7.4) It is desirable that the gas pressure that is sent to the user be kept constant. However,the gas

quantity consumed by the consumer fluctuates, while the amount of gas transferred from NGDW wells is constant. Due to this, it is necessary to control the quantity from NANGwells to respond to changes in the amount consumed by the consu;mer. Toaccomplishthis, a control valve is installed between the receiver tank and the blending tank, and it is controlled through PID computation performed from the deviation between the set-point and input value (pressure on the blending tank side).

(8) Lift gas flowrate, pressure control (Fig.7.5) The flowrate oflift gas that is injected into NGDN wells is always to be constant by using FCV (flowcontrol valve) for each well, and then in order to continue water lifting from NGDWwells, it is also necessary to control the pipeline pressure.

7-10

JX Nippon Oil8r Gas Exploration

Separator

/ PID Control

Unit

NGDl"

User

Fig. 7.4 Transfer gas pressure control

prD Control

PID Control Unit

Unit

High-selector

Unit

I I I

header

"'-----000411

.....----'---~)~

lift gas

Fig. 7.5 Lift gas flow and pressure control

For this reason, both the pressure and the flowrate of lift gas are controlled.

7-11


In the first place, PID control is conducted for each of pressure and flow rate. In other words, this control consists of two loops: one control loop for pressure that calculates the output value (MVl) from the deviation between the pressure set-point (SVl) and pressure input value (PVl) and the other control loop for flow rate that calculates the output value (MV2) from the deviation between the flow set-point (SV2) and flow input value (PV2). Either MVI or MV2, whichever is greater, is selected by a high selector, and then outputs it to the control valve. The valve used in this control loop is the type that closes when the output increases. Control is carried out in the direction such that the valve opening is made smaller according to the pressure and flow conditions.

(9) 200 kW gas compressor injection gas flow rate control (Fig.7.6)

prD Control Unit

Gas injection compressor

Fig. 7.6 Gas injection flow rate control

There is a method for controlling the injection gas flow rate which involves regulating the load of the compressor.

(10) Receiver tank pressure control (Fig.7.7) When the amount of gas used by the consumer fluctuates, the receiver tank at the Central processing station functions and changes in the transfer gas pressure are limited. However, if the gas flow rate supplied to the tank is not controlled, the tank pressure will become abnormal and regulation of the transfer gas pressure will become impossible. Although it is not necessary to keep the receiver tank pressure perfectly constant, the supply flow rate of gas must be controlled so that the above pressure is within a constant range. The gas produced by NANG wells is classified into lift gas, gas that goes into the receiver, and

7-12

JX Nippon Oil

It Gas Exploratio.n

injection gas. Of these, since lift gas is usually sent at a constant flow rate, for receiver gas control a method of regulating the production rate at NANG wells and that of regulating the rate of injection gas are available.

choke fElectrically-driven -.----------------- ------1 ,-_._- -_ ---------..

··· ·

I

•

I

-----,-------------------------------

,

.

•

--------------1

. .

,

r

,

Shut-down valve

........ - .. ---- -- - -----_

..

Gas injection compressor --. -_ ..----- ..- - -- _--_

• '

-_ .. -.

Gas injection

well

-

-_ .. --

---

---- - -- _ ----_

-

I

- ---

User Consumption

Fig. 7.7 Receiver tank pressure control

Currently, in the automatic

system at the Nakajo gas field, these two control functions are

provided and are used to respond to various conditions. The first method is applied to control the production at NANG wells, while the second method is used to control the capacity of gas injection compressors. Each will be described in detail below separately.

(11) Control of production rate at NANG wells As described above, the task of keeping the receiver tank pressure

virtually

constant

IS

performed to maintain constant gas supply conditions (between approx.O.85-1.45MPa). The production rate of wells is adjusted by using RM wells that permit remote control of the bean opening and SD wells that allow remote control of the shutdown valve, that operate manually from the central control room in accordance with the calorific value and quantity consumed by the consumers.

7-13

of sales gas


(12)Compressoremergencyshutdown at the North and South processingstations At the North and South processing stations, the 200kW transfer compressor increase NGDW gas at near atmospheric pressure to 0.6MPa. Although the capacity of the compressor is automatically adjusted by the suction (gathering) gas pressure, there are times during operation when the pressure of the suction (gathering) gas is vacuum and air will be mixed in through pin holes in the gas gathering pipeline, bringing about the risk of explosions. In this situation, just as"in the case of a blockage in the pipeline",when the gas gathering pressure drops too severely,continued operation of the compressoris dangerous. At times when conditions such as this occur, a built-in sequence immediately shutdown the compressor. In other words, when the oxygen density exceeds 0.3% or when the gathering gas pressure falls below -500 mmH20, a digital output signal is sent if the conditions continue for ten or more secondsto shut downthe compressor.

(13)Solenoidvalve control for supply switching Since supply air in the Central processing station is used to operate the air compressor,if there is an air compressormalfunction, the control system within the station will be adversely affe,cted. Therefore, when the pressure of the supply air falls, supply line gas is fed into the air line, thereby maintaining the pressure. In other words, when the pressure in the air line falls, a digital input signal is sent from a pressure switch. When this signal is received, a digital output signal is sent to open the solenoid valve. The line is thus designed so that gas will flowis.

7.3 Daily Report (1)Production report The daily report records the production of gas, The production rate at each NANGwell and the production rate for each total ofthe North district NGDWwells and the South district wells as well as the gas flowrate separated from oil by the stabilizer unit is recorded each hour. In addition to each daily production rate, the productionrate of oil from GOR(gas oil ratio) data by production testing is recorded and the water flowrate is also recorded. Sincethis production rate data on NANGwell is based on data taken from productiontesting, it varies from the actual production rate. Therefore, the rates for gas and oil that are received at the Central processing station are measured and proportionally distributed accordingto the production 7-14

JX .Nippon Oil It Gas Exploration

rates obtained from the production testing data.

(2)Well monitoring report The pressure at the NANGwell head along with the pressured in gathering gas lines is recorded every hour. This data enables changes in the production capacity of NANGwells to be monitored.

(3)Pipeline report The amount of gas used by each consumer,the lift gas rate to NGDWwells, and the transfer gas rate from wells are recorded by every hour and the total for each day is calculated each day and recorded.

(4) Injection gas report The injection gas rate is recorded each hour and the total for each day is calculated. In addition, the temperature and pressure at each part of the compressor and the pressure at injection wells is recorded, thus allowing monitoring of conditions at injection compressors and injection wells.

(5)Temperature monitoring report The IDH water temperature of NANGwells and the gas temperature at various points on the gas gathering pipeline are recorded, thus enabling monitoring of temperature changes.

7-15<


Chapter 8 : Well Drilling, Workover, Well Services 8.1 Review of 8.1.1

NK-66 (NANG), N21-5,6 &7 (NGDW) and NK-67(NANG)

NK-66 Well

Well, NK-66 was planned as horizontal well of side tacking from the existing 5-112"casing. The location of NK-66 was at NK-I0 base in central district of NANG(Non associated Natural Gas) field in attached, 1) Location of NK-66 Well. The target reservoir of NK-66 is Shiya formation, " The casing program was proposed as the order of 20", 13-3/8", 9-5/8* and q_-1I2"casingfor horizontal section in attached, 2) Well Schematic. For the purpose of drilling operation, JX Nippon Oil and Gas Exploration Co made a drilling contract with SK engineering and hired.rig, NE-2000./ In actually, the NK-66 was spudded in on 9th September 2012, ana. 26"hole section was drilled to 355m and 20" casing was immediately run to 347m. 17-1I2"holesection was continued to be drilled to 1,030m, and 13-3/8"casingwas set at 1,025m. 12~1I4hole section was drilled to 1,668m and 9-5/8" casing was set at 1,663m. 8-1I2"hole section was drilled to 2,185m as total depth(TD) and 5-1I2"casingwas set at 2,179m. For the purpose of the side tracking, the Whipstock in 5-1I2"casingwas set at 1,865m and made window at 1,865m for 5-1I2"casing. The sidetracking was immediately carried out in order to drill hori~~l-hole horizontal hole section to 2,120m ~Pth

on

9

th

and drilled

Novembe~.201~

Since the well was spudded in on 9th September, total operation days were 65days. The actual operational days, 65day?'were behind schedule for planned day,51days in attached, 3) Drilling Chart. The reason of the behind schedule was mainly due to hard to handle of BOP stack] spend time for reaming of hole and malfunction of electric logging and so on.

8-1


1) Location Map for NK-66 Well

o • •

NANG Wells NGDWWells OilWell.s

4

NK-66
8-2

JX 'Nippon Oil & GasExploration

2) Well Schematic

G.L. 30" Conductor @± 20m X-56, W/T:1.00"

20" is cemented to Surface

26"Hole to ±348m 20"CSG J-55, 106.5#, BTC

13-3/8" is cemented to Shoe

17-1/2"Hole to 1,030m 13-3/8"CSG N-80Q, 68#, BTC

12-1/4"Holeto 1,668m 9-5/8"CSG N-80Q, 40#, BTC

9~5/8" is cemented to the previous casing shoe

~'\.~ ,{o,£,.y;. "

~indow Cut @1(7~ 4-314"Hole to2_120~) Bare Hole

8-1/2"Hole to 2185m 5-1/t'CSG N-80Q, 17#, VAMTOP

5-1 It' is cemented to the previous casing shoe

8-3


3) Drilling Chart ••••••

o

- .::f- -~

-H-

NK-66H_Plan

--0- NK-66H_ActuaJ

-+-

;-+++-

-r2.00

+:2~

26"'TDat355m@12thSep2012

_+:

-+

Set20"CSG at3478m~

-+

-+- _,

-

IIJ~ =ft.

400

600

=i=i=l=::j::H$t$!=t~-:;+-:t:t.-~~'-'· =!=l= 3-

14th S:P2012

-- - R:: =t-=:L+

;; -

_ :

=::::. __

I

=t=l=+

'-

-

-_::g: l ~+:' ¥.

-t-

-+-

--~

R=

,,- ~n-

f-)-,

r-f-r ~- : "

800

1I,Ot}{)

~CD

m -;:: _ Ff:__ =~ -~ =E=f-=t= =i= - ~i=i=l= =t: ' I=~tt-~_· -~~$__ t:~t-i$~--t-+-$' ~;~~::':~·-~~-~~: __$~1~ ~_~~·~1~1;4:~:~~~~~~~Jf't ~~. W~j ·1

1,200

-H-+-

g

- ::t_++_

Q

~

-+- - --

-,--

r+

1,400

--

-+~-.--r.'--

-I~i=

-+-

- -+

~~'

H

= -

H~

- -

+-' ;-

c+++- _

-+ '

=t-~- ' , ,+-++-1--1- .. --+-'-.

Set9-518"CSGat1663m@9thOct2012 -I-j-

~= - -- - :~-,.

±

'_;==-

~--H-- -~.;"_H+ '=tt ~~~ - --t--t=I:--t::I=FF _ =:R= ~ -I-l=t- - - =t--!- -- =i= : =:=I-+.- - ::j:- -+ p-

.=

:±-ttJ - - q:-l=i:

-

i,SOO

+-

-+- c:::j=j::: -- -

-

__ ~ ++-_

•

1,600

-

=*:1:: ~~- -- :- : =$ Li=

-I=I=R:

+- --

_E __ f=-

-- -~=1=t=:

=t:

'~;:_':i::j: -- ~ r++- -;-+----

::j::

-~- - FaultTDSfrom 4th to 7th Nov 2012,

,

-+-+-

,-r-.

.setWhiPStocKat1l765.7m@30thOct2012 -1-- -T-

::-1:: --.+

::t=-

-=1=

2,000

=t: -

-t

+-I-H-++ 4-314"TDat2,120m@9thNov2012 S--1I2'"TDat2,lB5m@16thOct2012

-F-!:H-i--t-t-t--H::::t=i=j:

~

Set5-1I2'"CSGat2179m.@22ndOct2012

++-++2,400 10

15

I-H1-++

-

H-t

5

-

.,.~+__ §f$f:~tm~m~=:~I-=t=l=~-~~_ ~t=:tn:1

-t-

2,200

0

~

20

25

30

~

~

Daysfinm Spud

8-4

...-+, ~

",

~

~

Setcompl,etion@13thNov201l2

-+f=l+=i=++:j::j:=t=I=i=R=~

R:tf-:~

00

~

~

~

8.1.2

JX Nippon Oil It Gas Exploration

N21-5, N21-6 & N21-7 (Natural Gas Dissolved in Water: NGDW)

The purpose of drilling for the three wells, N21-5, N21-6 & N21-7 was to increase gas volume and iodine volume' and to make a further improvement for NGDW field(refer to attached No.1). In this fiels, drilling operation had not been carried out for last 50 years, and these three wells was drilled since 50 years ago. These wells would contribute further information of the characterize of NGDWfield. These three wells were drilled in N21base, respectively. Well,N21-5 was spudded in in March 2014, and the target was "Nishiyama" formation.( refer to attached No.1 Location Map) Prior to spud in of N21-5 in 2014, these three wells were designed as follows; •

Designing of Well, N21-5,6 &7

No.

Item

N21-5

N21-6

N21-7

1

Location

NGDWN-21base

NGDWN-21base

NGDWN-21base

2

Drilling Target

1,300m

3

KOPNertical

500m

500m

20"Condutor

20"Condutor

13-3/8"Casing

13-3/8"Casing

8-5/8"Casing

8-5/8"Casing

ESP(REDA)

ESP(REDA)

4 5 •

Casing

Completion

1,OOOm

1,200m 500m 20"Condutor

.

13-3/8"Casing 8-5/8"Casing <-

ESP(REDA)

Geologicalstructure Nakajo oil and gas filed is located in Tainai city of Nigata prefectural(Tainai city is 50km far for North direction from Nigata city). The concession is 13area for drilling operation, and there is 13 applicated concession, and 20%share holder of offshore concession. First well, R-l was drilled as Natural gas dissolved in water in 195~,

after

that, 7 bases(from NlO base to N16 base) at Soutt East direction of well, R-l with each 300m intervals, and further 7 bases(from N20 base to N26 base) at Soutt West direction of well, R-1 with each 300m intervals were constructed and drilled as Natural gas dissolved in water(NGDW). The base at Northwest side direction including well,R-l is called as North NGDW district, and the base at Southwest side direction

8-5

is called as South


~Ci1)~ district The targetted reservoir

IS

corespnding with Haizume and Nishiyama formation on

Nigata prefucture standard formaion lithology. From top side, the sand stone reservoir is distinighed from 5 reservoir to 15 reservoir. In the meanwhile, 10 reseroir is corespond with the top of Nishiyama formation, and the top of 15 reservoir is corespondwith 1)5of NonAssociated Natural Cias(NAN(j). About geologycalcircumastance, the geologicalstructure is situation which is slopped to Northwest side as single structure. and the structure is continuing to Tsuiji of NANGOil & Gas.

Regarding the produced brackish water, low temerature brackish water is from 5 reservoir to 8 reserovir, and modreate temperture is from 9 reservoir to 14 reservoir. and high temperature is from 15 reservoir. The targetted reservoir for this time is from 11 reservir to 14 reservoir( refer to attached No.2 Formation Lithology)

..

1) LocationMap

o

500

loi.oI

1000 1500 2000 2500m

......,

......,

1·57220

8-6

JX .Nippon Oil It Gas Exploration

2) Formation Lithology

"Nishiyama" Formation Target: 11+12reservoir (N21-6) 13 reservoir (N21-7) 14 reservoir (N21-5)

o

•

500

Opeation for Well, N21-5 The said well was spudded in on 25th March 2014, prior to spud in, 20"conductor pipe was

piled to 22m. ~

17-1I2"holewas drilled to 161m and set 13-3/8"casingwas set.

~

10-5/8"holewas drilled to 1,345m with several drilling problems. The followingproblems coused while drilling 1O-5/8"holesection 1) Lost circulation coused while drilling at 226~230mOost volume: 3kl), spotted lost circulation rnateril. 2)

Lost circulation caused while drilling at 444m(0.5kllhr), and lost circulation caused at 468m~498m(1.0~1.6kllhr).Total lost circulation caused at 499m.

3) While reaming down at 334m~499m, Down hole motor was malfunction dueto sand problem. 4) After kicking off at 507m, the bottom hole assembly was changed with two times. 8-7


5) The bottom hole assembly was changed with 3 times due to bit balling. 6) Lost circualtioncaused while drilling at 813m-892m(1.5-1.0kl/hr). 7) Lost circualtioncaused while drilling at 892m-1,01lm(1.0-0.5kllhr). 8) Lost circualtioncaused while drilling at 1,01lm-1,128m(0.5kllhr). 9) The bottom hole assembly was changed at 1,321mdue to bit, stabilizer balling. ~

Set 8-5/8"casinginside 1O-5/8"holesection.

~

Conducted completion and test.

•

Plan vsActual operaiton day for N21-5 Plan day for N21-5 was 32 days, on the other side, actual day was 39days. Actual day was

7days behiond for plan. Each job category is as follows; Job Categoly

No.

Plan

Actual

Difference

1

Prepare to Spud

1

1

2

Drill 17~112"Hole to 100m

3

3

3

Run and Set 13-3/8"CSG

4

6

° °2

4

Drill 10-5/8"Hole to 1500m

21

28

7

5

Run Electricalloggings

22

29

7

6


24

31

7

7

Clean up the Well

25

32

7

8

Completion

29

36

7

9

Test

32

39

7

(referred to the attached No.3)Drilling Chart)

•

Opeation for Well, N21-6 The said well was spudded in on 12thMay 2014, prior to spud in, 20"conductor pipe was piled to 22m.

~

17-1/2"holewas drilled to 161m and set 13-3/8"casingwas set.

~

10-5/8"holewas drilled to 1,023mwith several drilling problems. The followingproblems coused while drilling lO-5/8"holesection

1) The bottom hole assembly(BRA) was pulled in order to change for kick off assembly at 507m(Normalcondition, not drilling problem). 2) The BRA was pulled in order to change for the build up assembly at 604m(Normal condition, not drilling problem). 8-8

JX Nippon Oil" Gas Exploration

3) The BHAwas pulled due to bit balling at 641m. 4) The bottom hole assembly(BHA) was pulled in order to change for tangent assembly at 729m(Normal condition, not drilling problem). 5) The bottom hole assembly(BHA) was pulled in order to change for bit at 863m(Normal condition, not drilling problem). ~

Set 8-5/8"casinginside 10-5/8"holesection.

~


•

Plan vs Actual operaiton day for N21-6 Plan day for N21-6 was 29 days, on the other side, actual day was 17days. Actual day was 12days ahead for plan. Each job category is as follows; s

Job Categoly

No.

Plan

Actual

Difference

1

Prepare to Spud

1

1

0

2

Drill 17-112"Hole to 161m

3

2

-1

3


5

4

-1

4

Drill 10-5/8"Hole to 1,023m

19

14

-5

5


20

15

-5

6


22

17

-5

7

Clean up the Well

25

17

-8

8

Completion

26

17

-9

9

Test

29

17

-12

(referred to the attached No.41Drilling Chart)

•

Opeation for Well, N21-7 The said well was spudded in on

11th

June 2014, prior to spud in,

20"conductor pipe was piled to 20m. ~

17-1I2"holewas drilled to 161m and set 13-3/8"casingwas set.

~

10-5/8"holewas drilled to 1,209m.

~

Set 8-5/8"casinginside 10-5/8"holesection.

~


8-9


•

Plan vs Actual operaiton day for N21-7 Plan day for N21-7 was 24 days, on the other side, actual day was 18days. Actual day was 6days ahead for plan. Each job category is as follows; . Job Categoly

No.

Plan

Actual

Difference

1

Prepare to Spud

1

1

0

2

Drill 17-112"Hole to 161m

3

2

-1

3


4

4

0

4

Drill 10-5/8"Hole to 1,209m

13

14

1

5


14

16

1

6


16

17

1

7

Clean up the Well

17

18

1

8

Completion

21

18

-3

9

Test

24

18

-6

(referred to the attached No.5) Drilling Chart)

8-10


3)

Drilling Chart for N21-5

o

Days from Spud

o 25 March Spud in

20

30

- -j--r---Planned Operations

- -1_

200

-'--- ;... ---..... - --;--,..- - -

300

-;--- --..... - ~""-lil----

400

-,..- --:----i"t---

-

.; Prepare to Spud M 17-112" Hole to 100m Run. and Set 13-3 'S"CSG --,..-,..-.,.- -- -.- - ~ Dril11o..5'S" Hole to ljOOm Run Ele'Gt:ricallogltings Run and Se,t &-5'8"CSG ---- Clean up the Wen .. Completion Test -r----r-

13-3/8"CSG set :156m,

100

r- - -

....

40 Plan (mMDGL) days (cum.) 2~ 100 3 100 1 4 1350 17 21 J') 1350 1350 24 1350 25 1350 4 29 1350 n Depth

17-112"hole section: 161m 600 3700

o

~900 1000 1100 1200 1300 1400

--

j1Ct!;~~J:~E*5 '" jl:~~(O

mMDGL 504 514 523 533 958 1015 1063 1082 1130 1178 1226 1274 1331 1345 I

1.5 3 4.75 6

254 226 226 227

18 18 17.75 18 18 18 18 18 18 18

237 237 237 236 237 239 238 238 240 240

18

I

240

..

- -- -,. - -

_ __"'1 - - -

---

- - ---- - - - -- - - - - -- - - -'--,..- -

..

f--

1iii'i:("

)

r----f-

_ ... ---r-"

~timi <; _/

--

- - - -- -

- - --. - - - ---- - -.--

Esoo ~

--;--

- - - ----

__

.

..

;;;-;;t=;;;c -,;- '-

- --,..- - -

.

- - ~1~;;;~~-r-

-. -

-- - - - - -- - - - - -lO-5/8"hole final TD : 1,345m

--~~I~;..-

- -- - - - - -- - - - - -- - -- - - .......--- - - - -- - - - - -- - -

--

I - -~ -. -.-

- --

- - - - --

- ---

8-5/8"CSG set

1500

8-11

--

- - - - --

- - - - --

- -


4) Drilling Chart for N21-6

I

o

Days from Spud

I

o 12 May Spud in

20

17-112"hole section : 161m

30

40

~------------- ---------------------

100

--------------

200

----------

300

----------

400

------------ -------~---------------------~-----------------------------------------

500

--------------

600

------------------~-

....-------

13-3/8"CSG set (156.3m) & Cemening

------

---------------------

---------------------

---------------------

---~----------------

---------------------

---------------------

3700

o

&00

~

---------------------~--.-------------- ..... -

10-5/8"hole section: 1,023m

I

~900 1000

mMOGL

490

iJt;+t:~J~~.5 ftU=W)

l':

'J5"i"il;(O

....-~--~-~----~---------------------;

,--.~---------

325

8-5/8"CSG set

I

27 n_-'-=--+_-'=-'='-_+----=-2.:...7 ----I ,----------------

---------------------

tt---=--=--+_..:..::;.._+---=-2.=;._6---i

---------------------.;.---------------------;

26 26 26 26

,----------------

25 25

8-12

---------------------

•


5) Drilling Chart for N21-7

o

o

10

20

Days from

fcPud

40

Planned Operations

100 200

(rnBRT)

rrepare to Spud Prill 17-112"Hole to 100m k?unand Set 13-3/8"CSG - ........ ' -.,;.- .. -;.. ...- .. -.;.-;-..;-.;-+-;-......... -:0"- ':~-.; Drill10-5/8" Hole to 1500m EEf.3 Run Electricalloggings ~ Run and Set 8-5/8"CSG Clean up the Well -:0----1--1--;--_..---.--..-. ~~ Completion _.::-=. _,_ _ .. _ .. _ ...... _ .. _ .. _ ...... ~ ~_~~ Test

17-112"hole section:161m

I;;;;:;.~~~

13-3/8"CSGset

300 400 :-;:;.. .. _._~ .....

500 --1--+-+-1-_' - -"'_

5 Plan days (cum)

Depth

~i=-1=t

20 100 100 1200 1200 1200 1200 1200 1200

I

3 4 13 14 16 17 21 24

...-.-.--.

-+-1--1--1--+-+-1--1- -::__-I-+-I--I--I-

600 r--!--I--I--I--I--J......-...I.

poo "-c:t:r_j:~ ~ ~

.=!=

~--J-I--~~~i= -

E800

-

-!--!--!-~-!--

-

-

-'4r -

-o!--!--!--!-

-!--!--!--!o-!--!-::';_~I~=t=-t=:':-t.

-I-~

..- ...- ..-::-~

=-~~:-~-~--+=-"'i=':>-

"-'

Q

~900

= r- - c- -r--r---r-.---.--.-1000 ,..-- - -1-_.-1-+-1-_- -,., -1--1--+--' -

1100 :-=:-.-.. - ...-~-

...-

- l-t--1-1 .. ,::=:~.~ ~!-~!;:;'

10-5/8"hole section 1,209m

- c- -1--;---0--.--.---.r-

--t--t--I--t-I

-

-

--t-

,..._

1200

- ..-~~~~

'--I-I=I=E~Et

t-.-t-/f--t--I-l=i=

~~t--t-

..

to--tF.f

-t---t--f--f--t--f-·...

8-5/8"CSG set

f-

-Of-f-F+3-+-F+

..-......-..-.- ............ I~-t-t-t-

+-

I-t-t-t--i--f-l-I-I1-1-1--1---1-+

-'+-1-_-1-+-1--1-'-+-+-1--1-

1300 1400 1500

,___,__.___._._. - ._,.. ..- ...-;- .......- - - "-;- ...- --=tJ:.:1:_ - -;..-;- ...-;--;--;- ...-+-1-_..- ...-;-_ ..-';--;--;--1-...-+- ,..-;...- - ,..-,.... r-;-----;----

8-13


8.1.3

NK-67 (NonAssociated Natural Gas: NANG) Coming Well

The NK-67 well will be drilled on the NK-28 well pad. The well will produce on natural flow completion in the M layer of theShiiya Formation. Once the hole is logged and cased off with 5-1/2" casing, a Perforator will be run and Perforate into M layer of the Shiiya formation, Single completion will be run and set to maintain the oil and gas production. The well is planned to come on stream as soon as possible after completion and Xmas tree installa tion. The well is designed to provide additional information about the Shiiya reservoir. A proper pressure map for the Nakajo gas filed does not exist. Therefore the porepressure and fracture gradient profiles used in this program contain an error margin and the rig personnel must be alarmed for possible losses or kick that may occur while drilling this well.

'\

l.Name of Well

: NK-67

2.WellLocation

: NK-28 WELL SITE

3.Type of Well

: NATURALPRODUCTION ,

4.Expected Drilling Days

: 33 DAYS

5.Expected Completion Days

: 7DAYS

6.8-112"Hole 7.Total Drilling Depth

: 2,130.0 m (BGL)

8.True Vertical Depth

: 2,069.81 m (BGL)

9.Formation of Target

: M Layer of "SHIIYA"Formation

1O.TrueVertical Depth of Target

: 1,690.9-1,726.1 mSS

11.Expected Rotary Table Elevation

: -7.0m

12.UTMCo-Ordinate of Wellhead

(UTM ZONE 54) Latitude(Northing) : 4,212,183.0 niN Longitude(Easting) : 354,057.0 mE

13.UTMCo-Ordinate of Target eM Layer of SHIIYAFormation) (UTM ZONE 54) Latitude(Northing):

4,212,523.0 mN

Longitude(Easting):

354,673.0 mE

14.Directional Plan Type of Wellbore Trajectory

: S-Curve

Kick off point

: 390.0 m (BGL) 8-14

JX Nippon Oil & Ga.s Exploration

Max DogLeg

: 3.0 Degrees/30 m

Maximum

: 25.4 Degrees

Inclination

Displacement

: 351.6 m

Azimuth

: 63.4Deg (Relative to True North)

Lead

Angle

Before spudding -in, must be discussed carefully considering position of off set wells(NK-28 and NK-38 wells have been drilled on the NK-28 well site)

15. Hole Size, Terminal Depth (BGL) and Drilling RT-GL

-7.0 m

# ..

26"

±360.0 m

ROTARY

17-1/2"

±1,000.0 m

MOTOR

12-114"

±1,660.0 m

MOTOR

8-112"

±2,180.0 m

MOTOR

16. Casing Program and Set Depth (BGL) 30"

310 LBS/FT

X-56M WELD

24.7m

20"

106.5 LBS/FT

J-55

BUTTRESS

±360.0 m

13-3/8"

68 LBS/FT

N-80Q

BUTTRESS

±1,000.0 m

9-518"

40 LBS/FT

N-80Q

BUTTRESS

±1,660.0 m

5-112"

17 LBS/FT

N-80Q

VAMTOP.

±2,180.0 m

17. Mud program 26"

Gel MUD

SG 1.20

17-112"

KCL I LIGNATE MUD

SG 1.20 - 1.50

12-114"

KCL I LIGNATE MUD

SG 1.45 - 1.55

8-112"

KCL I LIGNATE MUD

SG 1.45 - 1.55

COMPLETION

KCL I LIGNATE MUD

SG 1.45 - 1.55

8-15


Drilling Chart

~ :2 :g

g :g

:E

~ ]_

0 en ..,.

E

.g

~ '"'"

>-

---

Cl

g

r-

eo

~

~

Z

~

..... m s:

~

<..(.)

~

C)

C

"i::

o

<=> 0 co

<=>

<>

~

<=> N

<=> <=>
g_

CU:f8Ul)

.s:

a

~

Q)

~ ~«

~

§

0c::;

i

1

///af////'

ft::*4//' ~)}//, //n////,

~o

~ ~

",(.9

:§~

~

"0

::;;;

j

.~

6j

I'il

R:

~o

"0

~ ~

Zll g

~

N

101

w

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JX Nippon Oil & Gas Explorat:ion

8.2 Workover Reason to perform a work over Workovers rank among the most complex,difficult and expensive types of wellwork. They are only performed if the completion of a well is terminally unsuitable for the job at hand. The production tubing may have become damaged due to operational factors like corrosion to the point where well integrity is threatened. Downholecomponents such as tubing, retrievable downhole safety valves, or electrical submersible pumps may have malfunctioned, needing replacement. In other circumstances, the reason for a workover may not be that the completion itself is in a bad condition, but that changing reservoir conditions make the former completion unsuitable. For example, a high productivity well may have been completed with 5Y2"tubing to allow high flow rates (a narrower tubing would have unnecessarily choked the flow).Some . years on, declining productivity means the reservoir can no longer support stable flow through this wide bore. This may lead to a workover to replace the 5Y2"tubing with 4Y2"tubing. The narrower bore makes for a more stable flow. Operation Before any workover, the well must first be killed. Since workovers are long planned in advance, there would be much time to plan the well kill and so the reverse circulation would be common.The i;;_tensenature of this operation often requires no less than the capabilities of a drilling rig. The workover begins by removing the wellhead and possibly the flowline, then lifting the tubing hanger from the casing head, thus beginning to pull the completion out of the well. The string will almost always be fixed in place by at least one production packer. If the packer is retrievable it can be released easily enough and pulled out with the completion string. If it is permanent, then it is commonto cut the tubing just above it and pull out the upper portion of the string. If necessary, the packer and the tubing left in hole can be milled out, though more commonly,the new completion will make use of it by setting a new packer just above it and running new tubing down to the top of the old. Workovers on casing Although less exposed to wellbore fluids, casing strings too have been known to lose integrity. On occasion, it may be deemed economicalto pull and replace it. Because casing strings are cemented in place, this is significantly more difficult and expensive than replacing 8-17


the completion string. If in some instances the casing cannot be removed from the well, it may be necessary to sidetrack the offending area and recomplete, also an expensive process. For all but the most productive well, replacing casing would never be economical.

8.3

Well Service Well services is a department

within a petroleum production company through which

matters concerning existing wells are handled. Having a shared well services department all (or at least multiple) assets operated by a company is seen as advantageous

for

as it allows the

pooling of talent, experience and resources for managing wells. The term may sometimes be used to encompass the larger section of the industry responsible for wells including the supplier companies as well the operating company's wells department.

Remit A well is initially drilled and completed under the control of the drilling and completions department

operating under the request of the asset. Once the well is completed, control is

transferred

to the asset's production team, who will operate the well as appropriate

purposes. Should any issues of well integrity or any requirement will refer the issue to the well services. During interventions,

for their

for well work arise, the asset

control of affected well is handed

over from production to the well services crew at the well site, a practical action involving transferring

control lines from the production control panel to the well services control panel.

Structure When well work is required, it is the responsibility

of the WOE to assemble the team and

arrange their dispatch to the well site. The team will consist of a well services supervisor and other operators. The well services supervisor is a dedicated worker who is sent to oversee well services operations at well sites and take responsibility

for all well services personnel. At

offshore sites, there will commonly be two, to cover both day shift and night shift. The other operators will usually consist of personnel from supplier companies, who are trained in the relevant field, such as wireline, coiled tubing, wellhead maintenance,

8-18

etc.

.


Chapter 9: Facility Maintenance of NAKAJO Oil and Gas Field

) _ r

:

T ()

r:

9.1 Facility Maintenance Control I make ISO Manual in a place based on IS09001 which is a standard of quality management systems by the ISO (International Organization for Standardization) and apply it to secure supply, gas, crude oil, quality of iodine to sell for a user in NAKAJO, and maintenance, the check of a periodical plant (management facilities) is carried out based on this. "The maintenance check standard" that showed the management facilities name, check contents, a check method, check frequency is established to maintain the performance of the plant continuously in ISO Manual in the place. When abnormality is discovered by check or when something wrong is recognized in operating conditions, performs the repair by the company and/or by the outside order. Main maintenance, check carried out regularly in each workplace is showed as below. ~ntenance

G;

(1)American regulator periodic inspection (2) Periodic inspection (well head, heater) of production oil equipment (3) Periodical opening and closing check the valve of the wellhead base (4) Periodic inspection of a separator for natural gas dissolved in water, KANSUi (the

water produced with dissolved gas) waterway and the outlet port (5) Periodic inspection of a KANSUI (the water produced with dissolved gas) waterway

and the pipeline (6) Lift pipe check of wells for natural gas dissolved in water (7) Check of a little dangerous materials amount to be stored

(8) Leak check of the pipeline (Gastec) (9) Periodic inspection (draining water device, water seal valve) of the pipeline (10) Thickness gauging of the pipeline (11) Periodic inspection of whist

(12) Check of the valve in the pit Wells Gr (1) Check and maintenance of the drilling equipment Natural gas dissolved in water Gr 9-1


(1) Periodic inspection of Glycoldehydrator for Natural gas dissolvedin water (2) Check and maintenance of the compressor for Natural gas dissolved in water (3) Check of fire extinguishing facilities (4) Check of a little dangerous materials amount to be stored

Central processing plant and Gas compressor station Gr (1) Check of production oil equipment

(2) Check of the oil storage tank (3) Check of CENTUM (4) Check of the Seismometer (5) Check of the instrumentation apparatus (6) Check of a little dangerous materials amount to be stored (7) Check of fire extinguishing facilities (8) Check of the 200KWcompressor (9) Check of the 260KWcompressor (10) Check of the infrared sensor (11)Check of lTV (industrial surveillance camera) Facilities Gr (1) Check of the oil storage tank (2) Check and maintenance of the telecom telemeter (3) Check of UPS (4) Check and maintenance of the electric apparatus (5) Check and maintenance of the instrumentation apparatus (6) Check of the electrical generator for emergency (7) The measurement of the leak current (8) Check of the radio machine (9) Check of the company house electric circuit (10) Check of electric facilities-proof (11)The measurement of the electricpotential-proof (12)VDT environmental measurement result and lighting equipment check I introduce maintenance and check contents about the maintenance of

CD

Lift pipe

check of wells for natural gas dissolved in water and @Check of the 200KWgas compressor among the above.

9-2

@c JX Nippon

CD


Lift pipe check of wells for natural gas dissolved in water In the case of periodical repair, Lift pipe check of wells for natural gas dissolved in

water is carried out once a year. The purpose of lift pipe check is to confirm the follows. · The damage or not damage to lift pipe · The plug or not inside lift pipe · The outsidelinside condition of the well-head equipment. The work procedure is as follows. (1) Preparations before work (2)Pull out of hole pipe operation (3)Lift pipe maintenance (4)Running in hole pipe operation (5) Summary of putting in order and the work record

Figure 9.1-1

State of lift running in hole operation

9-3


State of the lift pipe maintenance

Figure 9.1-2

@ Check of the 200KW gas compressor For the check maintenance maintenance

of the 200kW gas compressor, there are voluntary

to perform every 2,000 driving time and maker maintenance

to

perform every 8,000 driving time. The purpose of these check maintenance

confirms whether a valve and the cooling

line do not have damage and this is because it changes a part.

The work procedure of the voluntary maintenance (1) Interception

is as follows.

of the main switch

(2) Discharge valve disassembly, assembling (3) Inhalational

valve disassembly, assembling

(4) Oil-extracted of the outside oil filter (5) Intercooler strainer cleaning (6) Confirmation of the cylinder, piston and the oil leak of the grand packing (7) Check of the pressure gauge and thermometer (8) Check of the motor connection point coupling, bolt and the slack of the nut

9-4


(9) Check of compressor, foundations of motor, bolt and the slack of the nut (10) Check of the leak of the coolant pipe (11)Compressor pressure test (12)Discharge valve maintenance (13) Connection of the main switch

.. _

Figure 9.1-3 gas compressor

9.2 Facility Maintenance, Repair & Rental Repair and the update of the plant are carried out based on a result of the periodical check mentioned above. In addition, repair and update is carried out urgently when a plant is damaged by troubles. I introduce an example of repair and update carried out in late years.

CD

Repair of the pipeline Because the leak from a pipeline caused by the exterior corrosion occurred, I

changed a part. The work procedure is as follows. (1) De-pressure

(2) Digging and identification of the leak point (3) Pipe inside washing (4) Cutting (5) Welding 9-5

JX Nippon Oil & Gas Explorat.ion

(6) X-ray check (7) Leak test (8) Pressurization

Figure 9.2-1

Pin hole which occurred in a pipeline

9-6


Figure 9.2-2

State of the laying of the new pipe

@ Update ofthe pipeline Because it passed more than 30 years after laying pipe and, plural leak from a

-

.

pipeline caused by the internal corrosion and exterior corrosion occurred, I updated it. The work procedure is as follows. (1) Plan (2) Digging (3) Welding (4) Leak test (5) Connecting to the existing line (6) Pressurization

9-7

o JX Nippon Oil & Gas Exploration

Figure 9.2-3 State of an existing pipe (the left) and the new pipe (the right)

®

Well casing for natural gas dissolved in water repair Because leak caused by the corrosion occurred, a casing of well for natural gas

dissolved in water cut this part and performed repair to connect a new casing. A part contacting with a water vein at 10m depth under the ground is damaged by the corrosion. The work procedure is as follows. (1) Disassembly of neighboring facilities (2)YAlTA(sheet piles) piling (3)Digging (4) Cutting (5)Welding (6) Backfill (7)Assembly of neighboring facilities

9-8

JX Nippon Oil & Gas Ex loration

Figure 9.2-4

State of the YAlTA (sheet piles) piling work

Figure 9.2-5

State after the digging

9-9


Figure 9.2-6

the casing which I cut

9-10

~

JX Nippon Oil It Ga.s Exploration

Chapter 10 : Iodine Factory in Nakajo Oil & Gas Field 11.1 Characteristics of Iodine The Iodine, a halogen, occurs sparingly in the form of iodides in KAN-SUI (brackish water), which is produced with dissolved gas at a concentration of 75 milligrams per liter. The crude Iodine is recovered from KAN-SUI and exported to customers worldwide.

Product Specifications (Nakaio): Purity More than 99.7% Non-VolatileMaterials Less than 0.05% Sulfate Less than 0.02% Chlorine/BromineLess than 0.005% Iodine Atomic No. Melting Point Boiling Point Density

: 53 : 113.6°C : 182.8°C : 4.93 g/cm

Iodine

Fig. 11.1 Elemental Periodic Table and Specificationsof Nakajo' Product 11.2 Various Uses of Iodine The Iodine has a wide variety of uses in our lives. The main areas of use include the medical field such as X-ray contrast media and gargles, sterilizers, fungicides, feed additives, photo-sensitizers and polarizing films for liquid crystal displays. . .

10-1

JX Nippon Oil & Gas Exploration Herbicides

2%

Salt additives

4%

Stabilizers

6%

Feed additives

7%

LCD

24%

10% ---

Pharmace utlcats

Antimicrobial ag.ents

17%

11% catalysis

*

16%

By Kanto Natural Gas DevelopmentCo. Ltd.

Fig. 11.2Various Uses ofIodine 11.3 Production of Iodine in the world, Japan and Nakajo field Iodine is a nonmetallic element, and only is extracted from the natural resources. Iodine is present in the sea water and soil. Currently, the worId production of iodine

IS

conducted only in areas where the iodine

concentration is high in caliche from the Chile nitre and brines from the Natural Gas dissolved in water field such as Japan. The iodine production in Japan covers as much as approx. 30%of the total iodine production in the world. And then the iodine production of Nakajo field is approx. 3% of the total iodine production in the Japan.

• Russia China

USA

Azerbaijan

•

Turkmenistan

•

Chile

Indonesia

:8: By Kanto Natural Gas DevelopmentCo. Ltd.

Fig. 11.3 Map of Iodine Producing Countries 10-2

0c JX Nippon

Oil & Gas Explorat.ion

Supplier: : 31 ,000 t (Year 2012)

Total Production Chile

: 18,500 t (60%) : 10,000 t (32%)

Japan Nakajo

300 t ( 3%)

IDA Production Facilities of Iodine Factory The Iodine is extracted from the KAN-SUIby means of the blowout method.

CD

The KAN-SUI is fed to the mixing tanks where an oxidant is added.

~

The mix fluid is fed to the Blowing Tower where the iodine is evaporated into the air by 2 blowers.

® The Iodine in air is absorbed with a reducing agent in the Absorbing Tower, leading to the absorbent solution. The Iodine is crystallized using an oxidant, melted to remove impurities, cooledto solidify,then flaked and packed into the drums.

..

..

Oxidation

KAN-SUI

Melting & Cooling

NGDW wellpads Blowing

& Absorbing

Towers

Fig. lO.4-i Production Flow

10-3


odine Process Flow Diagram fHydrochlor ic acid J

fSuIfur ic acid J

fSodium hydrogen sulfite J

fSodium hyooch lor i tej

I

NaCIO

:---------1111, Gasify

fChlorineJ CL

(Iodine Molecule)

/ .=====z...,-,

/t"" /

Absorbing

I)

~I" Solution

120'C Heating

Impurities

Tanks Melt! liquefy

Orainage ...... __ --1

Iodine Oxidation ReleaseReaction

Iodine absorption Reaction

Iodine Separation

Fig. 10.4-2Iodine Process Flow Diagram

10-4

Iodine Products

Iodine Refinement

@t


Appendix 1

HSE of Nakajo Gas & Oil Field

Appendix 1: HSE of The Nakajo Oil and Gas Field Chapter 1

HSE rule ofThe Nakajo Oil and Gas Field

The Nakajo Oil and Gas Field is divided into Nakajo mine of the oil, natural gas business and Crude iodine factory of the Crude iodine business by a product and each competent authorities are Regional Industrial Safety and Inspection Department in charge ofMinistry of Economy,Trade and Industry and High-pressure gas security man and a person in charge of Pharmaceutical affair instruction of Niigata prefectural government office. The laws and ordinances applied about safety vary according to business and Operational Safety Rule is prescribed as follows with each application laws and ordinances. 1. Nakajo mine (oiland natural gas) Operational Safety Rule (MiningSafetyAct) 2. Nakajo iodine factory (Crude iodine) (1) High-pressure gas hazard prevention regulations (High Pressure Gas Safety Act) ( 2)

Poison, dynamite hazard prevention regulations (Poisonous and Deleterious

Substances ControlAct) Here, explain the summary of Operational Safety Rule ofthe Nakajo mine which is oil and natural gas business in a followingchapter.

Chapter2

Operational SafetyRule

1. General rule (1) Purpose

It determines the protection ofthe worker, prevention ofthe work-related accident and the environmental disruption caused by mining to secure safety. (2) Use

I carry out the activity to secure safety basically by a cycleof a plan, do, check, and action. ( 3 ) Observance duty All miners must followthese officialregulations. 2. The contents that it is prescribed that I establish it in Operational Safety Rule legally (1) Safety management systems Al-l

CD

Organization for safety management: I elect a general safety controller, safety controller and a safety supervisor in consideration of an organization in the company to carry out securing of safety systematically.

@ Safety and health Committee: I install

it to do an investigation,

the deliberation

and a report

about an

important matter about safety and carry out the hearing of the opinion toa miner, the notice to a miner and discussion. I elect half of committees from a miner. (2 )

The enforcement of the present situation investigation (risk assessment)

( 3 ) Activity to promote safety: 1 build Safety management

systems by the PDCA cycle. to promote safety and

devise the enforcement point appropriate to each mine. The example of the safety promotion activity of this field is described in Chapter 3. (4)

Safety education: About safety education to carry out when a miner works, I establish the following content.

CD

Work which need safety education and education contents

@ The qualification that safety education is exempted from (5)

CD

Emergency response In any of the report matter(a

serious accident, a disaster) to establish in rule

Article 45 and Article 46, I report it with emergency communication

chart

established promptly.

@ It determines a method of initial response and the evacuation.

®

I set up the organization for state of emergency measures and a task force.

@ It determines afflicted people relief.

®

I perform analysis and the preventive measures against contents of accident and disaster

(6) The measures that mining industry incarnation should take measures The disposal of gas, the use of a machine,

an appliance

and equipment,

the

handling of explosives, the relief at the time of the disaster, processing of mining industry waste, well waste water and the smoke from a mine, digging of the land, a round of inspection and check (7) The training and visit Securing of safety of the trainee and the visitor ( 8 ) Measures for prevention of other hazard

CD

Prevention of the hazard in the work

Al-2

Measures

during a high place, heavy industrial

machine work, the prevention

of

the electrician crops electric shock and construction interruption @ Prevention of the traffic accident in check rounds of inspection (9) Review the evaluation method of measures to secure safety and measures And builds the system which a general safety controller is in charge of a situation investigation.

Chapter 3

PDCAfor safety of The Nakajo Oil and Gas Field

The Mine Safety Act was revised in 2004. As revised content, a major deregulation from old law was performed and introduced a way of thinking (present situation investigations) of the risk management and it was with the rule systems which put an important point for the independent safety measures of the mine more such as the construction of the safety management system by the PDCAcycle. Here, Main contents of safety PDCAof this field is as follows. 1. Health, Safety and Environmental management policy A general safety controller decides Health, Safety and Environmental policy every year and makes order of implementation. The main point of the policy of 2015 is as follows. (1) I understand JX Group Mission Statement (cf. document 1) and our HSE policy (document 2) enough. ( 2) In each workplace, I devise effective action plan on the basis of the actual situation of the workplace and achieve an aim by the steady practice. (3) I set following three points as an important point item of HSE CDThereinforcement of disaster precautionary measures (correction of the potential danger place, thorough safety awareness) Active utilization ofthe HIYARI-HATTO(near miss accident) @ Thorough health care.

®

Promotion of environmental measures

(4) I always have an awareness (Ethics:) of JX group employee and keep in mind with

legal compliance in the everyday life. 2. Active use of HIYARI-HATTO(near miss accident) I carry out the following measures to realize the active use of HIYARI-HATTO(near. miss accident) performed by the Policy mentioned above. (1) I establish a commendation system for an annual majority reporter (to the higher Al-3

third place) and am conferred a testimonial

and the prize money in front of all

staff members. (2) The workplace group comment of HIYARI-~TTO(near

miss accident) report from

each person is performed basically by positive finding. (3) HIYARI-HATTO(near

miss accident) report is developed by an email in a mass

regularly to all staff members. (4) I carry out the measures motivation

of HIYARI-HATTO (near miss accident) surely and the

of reporting it is roused to each person by keeping the utility of the

report. ( 5)

I gather

HIYARI-HATTO(near

mISS accident)

III

the year

and analyze

the

tendencies of contents. A result, the number of reports of 2014 became 106 cases and grew 43 from 63 cases of 2013.

3. Training for emergency response I carry out the training that all staff members participate

in for emergency response

once a year including head office task force and, through a follow-up ofthese training, push forward the construction of the oil and gas field which is strong in a disaster. As training content of 2014,

for the assumption that fire of the oil and gas well base,

the strong sulfuric acid leak of the iodine factory and the injured person outbreak of an employee

during

occurrence realized

device check

of seismic intensity

appropriate

communication

action

was

happened

5", training

was performed.

to each accident,

(intention transmission)

force again. After these training

successively

certain

by "an earthquake By these

safety

training,

confirmation,

I

quick

and the cooperation with the head office task

ended, I cope for 18 points of improvement

matters

pointed out one by one.

4. Safety meeting before periodical repair construction and Rules training all at once I perform a safety meeting in the cause of the participation

(29 people participate

the results from 24 companies in 2014) of all subcontractors

in

before periodical repair

construction which is no steady work largest in this oil and gas field, every year. The purpose of a safety meeting is follows

CD ®

I publicize a HSE policy of this oil and gas field Prevention

such

as

work

conflicting

by

communalizing

periodical

repair

construction schedule of each group, and doing a horizontal connection thickly.

®

Close cooperation

by the good communication

Al-4

between

the people concerned

including a subcontractor, We think that this meeting contributes to accident prevention of the no steady work.

5. Mine safety week Ministry of Economy, Trade and Industry set (from 1 to 7 on July) for whole country mine safety week on "day (July 1) of the nation contributing

to prevention

of a mine disaster

security" for the purpose

and the

mining

of

environmental

disruption by promoting the voluntary safety activity in the mine and planning uplift of the safety awareness. To it, I perform the event of the week premeditatedly

every year in this oil and gas

field. The special safety round of inspection of the president, the lecture by TAl Al police station road safety section manager and other company plant tour were performed for planning uplift of the safety awareness. In addition, review and improve the contents of an action plan through a follow-up after the end every year, too.

6.

Safe & Health Committee

I hold a Safe & Health Committee as a member in a safety controller, a production manager, Section Manager of general affairs, the maintenance and dissolved gas charge senior staff and the representatives of the miner of four others as the chairperson in people of general safety controller every month. An important matter concerned with the safety such as HSE policy,HSE management action plan, follow-up of that action plan and present situation investigation is discussed in Safe & Health Committee. In addition, the main content reviewed in the committee is as follows. (1) The achievement situation of HSE results (annual aims of the nonstop operation disaster such as 0) (2) The presentation situation of HIYARI-HATTO(nearmiss accide?t) report (3) Pointed matter by the workplace rounds of inspection of production and each wellsite base (4) Follow-upprogress of the emergency response training ( 5) the report from each committee such as 5S and careful driving promotion committee.

Chapter 4

Others Al-5

1.

EMS activity

Based on the JX group EMS guidelines, I am based on EMS promotion Committee and carry out EMS activity. About the greenhouse gas reduction, it becomes the environmental

aim of the company

and carries in particular out measures for accomplishment energetically.

2.

Health activity

The health

activity of this oil and gas field is carried out in culture

and sport

Committee. I carry out the competition of softball and a tennis and a bus ski trip for the purpose

of

CD

mental

health

care and health

making

exercise and @ the

aggressive development of promotion event in culture and sport Committee.

3.

1S09001

This oil and gas field acquires 1S09001 of the product

quality

management.

I

advocate "the stable operation" as one of the quality policies and assume essential "no disaster without an accident" quality target for the practice. A quality policy, quality target of 1809001 of this oil and gas field shows in document 3.

List of documents

Documentl. JX Group Mission Statement Document2. HSE Policy Document3. 1809001 quality policy, quality target

Al-6

JX Group Mission Statement

[JX Group Slogan]

The Future of Energy, Resources and Materials [JX Group Symbol]

[JX Group Mission Statement]

JX Group will contribute to the development of a sustainable economy and society through innovation in the areas of energy, resources and materials.

[JX Group Values]

Our actions will respect the EARTH.

Ethics

A dvanced ideas Relationship

with society

Trustworthy

products/services

Harmony

with the environment

HEALTH, SAFETY and ENVIRONMENTAL POLICY OF JX NIPPON OIL & GAS EXPLORATION CORPORATION

General Policy We, ]X Nippon Oil & Gas Exploration Corporation, as a member of JX Group, whose mission statement is to contribute to the development of a sustainable economy and society through innovation in the areas of energy, resources and materials, are undertaking oil and gas exploration and production operations as one of the core businesses of JX Group. We, as a member of the society, are committed to providing oil and gas for the society's needs in a manner that avoids injuries and illnesses to our employees, contractors and neighbours while acting in armony with the environment of the Earth.

Strategies We implement this policy by conducting the following strategies: • • • • •

• •

Ensuring that Health, Safety and Environment (HSE) considerations are given prevailing status over our other business considerations. Ensuring compliance with all relevant legislations and other requirements to which we subscribe. Applying a systematic approach to HSE management to achieve continual HSE performance improvement including setting strict HSE objectives and performing regular audits and reviews. Designing our workplaces to minimise the risks to personnel and developing work practices to further reduce the risks as low as reasonably practicable. Encouraging the use of the best available technology to reduce the impact of our operations to the environment, particularly with regard to the efficient use of energy and materials, the minimisation of waste and the prevention of pollution. Ensuring our personnel to be competent for their tasks and further providing HSE training and awareness programmes to mana.ge HSE risks. . Developing communication channels to ensure the HSE policy and its objectives are understood by all our personnel, contractors and customers, and to actively seek their input and feedback.

Application 'The President of JX Nippon Oil & Gas Exploration Corporation is accountable for ensuring the HSE policy is implemented and that its effectiveness is reviewed annually. All personnel and contractors of our Group Companies in all areas of the activities under our operational control are responsible for applying the HSE Policy.

Shunsaku Miyake Representa tive Director, President and CEO JX Nippon Oil & Gas Exploration Corporation June 2014

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Appendix 2

Drilling Program for Well, NK-67

)


Appendix 2: NK-67 (NonAssociated Natural Gas: NANG) Coming in 2015 CONTENTS [1]

Drilling Summary Operation Organization Chart · Drilling Summary · Drilling Chart · Time Estimation · Well Schematic · Completion Well Profile

[2]

Geological Data · Contour map

"

· Forecast Formation Top · Formation Pressure & Temperature Prognosis [3]

Well Plan · Well Trajectory

[4]

Job Out line

[5]

Completion and Flow test

[6]

Detailed job instruction · BHAList · Bit Program(BHI.) · Casing & Centralizer Program · Mud Logging and Electrical Logging Program

[7] Others . Completion program · Wellhead specification

A2-1


[1] Drilling Summary Operation Organization Chart

Well Site

Oifice Opeiratialill"'ana~ Mt lslilig;e Draling SUlpenn_dent

lfKhniiQI Support

Pf"(Ji~t e:oordinatrli)QI & alili~jn~5

r. r. H. Wa'hUHlOO

~ OIwflopm.m Ot!pL.4.

A2-2


Drilling Summary The NK-67 well will be drilled on the NK-28 well pad. The well will produce on natural flow completion in the M layer of the Shiiya Formation. Once the hole is logged and cased off with 5-112"casing, a Perforator will be run and Perforate into M layer of the Shiiya formation, Single completion will be run and set to maintain the oil and gas production. The well is planned to come on stream as soon as possible after completion and Xmas tree installation. The well is designed to provide additional information about the Shiiya reservoir. A proper pressure map for the Nakajo gas filed does not exist. Therefore the pore pressure, and fracture gradient profiles used in this program contain an error margin and the rig personnel must be alarmed for possible losses or kick that may occur while drilling this well. NAME OF WELL

: NK-67

WELL LOCATION

: NK-28 WELL SITE

TYPE OF WELL

: NATURAL PRODUCTION

EXPECTED DRILLING DAYS

: 33 DAYS

EXPECTED COMPLETION DAYS

: 7DAYS

8-112"HOLE TOTAL DRILLING DEPTH

: 2,130.0 m (BGL)

TRUE VERTICAL DEPTH

: 2,069.81 m (BGL)

FORMATION OF TARGET

: M LAYER OF SHIIYA FORMATION

TRUE VERTICAL DEPTH OF TARGET

: 1,690.9 - 1,726.1 mSS

EXPECTED ROTARY TABLE ELEVATION

: -7.0m

UTM CO-ORDINATE OF WELLHEAD (UTM ZONE 54) LATITUDE (NORTHING) : 4,212,183.0 mN LONGITUDE (EASTING):

354,057.0 mE

UTM CO-ORDINATE OF TARGET eM LAYER OF SHIIYA FORMATION) (UTM ZONE 54) LATITUDE (NORTHING):

4,212,523.0 mN

LONGITUDE (EASTING):

354,673.0 mE

DIRECTIONAL PLAN TYPE OF WELLBORE TRAJECTORY

: S-CURVE A2-3


KICK OFF POINT

: 390.0 m (BGL)

MAX DOG LEG

: 3.0 DEGREES/30 m

MAXIMUM INCLINATION

: 25.4 DEGREES

DISPLACEMENT

: 351.6 m : 63.4 DEG (RELATIVE TO TRUE

AZIMUTH

NORTH)

LEAD ANGLE BEFORE SPUDDING-IN, MUST BE DISCUSSED CAREFULLY CONSIDERING POSITION OF OFF SET WELLS. (NK-28 AND NK-38 . WELLS HAVE BEEN DRILLED ON THE NK-28 WELL SITE.) HOLE SIZE, TERMINAL DEPTH (BGL) AND DRILLING RT-GL

-7.0 m

26"

±360.0 m

ROTARY

17-112"

±1,000.0 m

MOTOR

12-114"

±1,-660.0 m

MOTOR

8-112"

±2,180.0

MOTOR

ill

CASING PROGRAMME AND SET DEPTH CBGL) 30"

310 LBS/FT

X-56M WELD

24.7m

20"

106.5 LBS/FT

J-55

BUTTRESS

±360.0 m

13-3/8"

68 LBS/FT

N-80Q

BUTTRESS

±1,000.0 m

9-5/8"

40 LBS/FT

N-80Q

BUTTRESS

±1,660.0 m

5-1/2"

17 LBS/FT

N-80Q

VAMTOP

±2,180.0 m

MUD PROGRAMME 26"

Gel MUD

SG 1.20

17-112"

KCL I LIGNATE MUD

SG 1.20 - 1.50

12-114"

KCL I LIGNATE MUD

SGl.45 - 1.55

8-112"

KCL I LIGNATE MUD

SG1.45 - 1.55

COMPLETION

KCL I LIGNATE MUD

SG 1.45 - 1.55

A2-4


Drilling Chart

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A2-5


Time Estimation NK-67 Time Estimation 2015.03.02 ... Job Acc. NO.

Job duration From

To

Job Time

Job Description

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A2-6


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A2-7

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A2-8

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0X JX Nippon

Oil & Ga.s Ex!ploration

JX Nippon Oil & Gas Exploration CO NK-67

o

Measured

Angle

Azimuth

TVD

Depth

Deg

Deg

m

0.00

0.000

0.000

Rectangular Coordinates m 0.00

Vertical

Dog

Section

Leg

0.00

0.00

0.00

0.00

0.00

0.00 0.00

30.00

0.000

0.000

30.00

0.00

0.00

2

60.00

0.000

0.000

60.00

0.00

0.00

0.00

3

90.00

0.000

0.000

90.00

0.00

0.00

0.00

0.00

4

120.00

0.000

0.000

12.0.00

0.00

0.00

0.00

0.00

5

150.00

0.000

0.000

150.00

0.00

0.00

0.06

0.00

6

180.00

0.000

0.000

180.00

0.00

0.00

0.00

0.00

7

210.00

0.000

0.000

210.00

0.00

0.00

0:00

0.00

8

240.00

0.000

0.000

240.00

0.00

0.00

0.00

0.00

9

270.00

0.000

0.000

270.00

0.00

0.00

0.00

0.00

10

300.00

0.000

0.000

300.00

0.00

0.00

0.00

0.00

11

330.00

0.000

0.000

330.00

0.00

0.00

0.00

0.00

12

360.00

0.000

0.000

360.00

0.00

0.00

0.00

0.00

390.00

1.000

63.360

390.00

0.08

0.16

0.17

1.00

0.49

0.97

1.09

1.50

13 14

420.00

2.500

63.360

419.98

15

450.00

4.000

63.360

449.94

1.25

2.49

2.79

1.50

16

480.00

5.500

63.360

479.83

2.37

4.72

5.28

1.50

17

510.00

7.000

63.360

509.65

3.83

7.63

8.54

1.50

63.360

539.38

5.64

11.25

12.59

1.50 1.50

18

540.00

8.500

568.99

7.81

15.56

17.41

63.360

598.46

10.32

20.56

23.00

1.50

63.360

627.77

13.17

26.25

29.37

1.50

63.360

656.91

16.37

32.62

36.50

1.50

39.68

44.39

1.50

47.40

53.04

1.50

570.00

10.000

63.360

20

600.00

11.500

21

630.00

13.000

660.00

14.500

19

22 23

690.00

16.000

63.360

685.86

19.91

24

720.00

17.500

63.360

714.58

23.78

25

750.00

19.000

63.360

743.07

28.00

55.80

62.43

1.50

26

780.00

20.500

63.360

771.31

32.54

. 64.86

72.57

1.50

63.360

799.27

37.42

74.58

83.44

1.50 1.50

27

810.00

22.000

28

840.00

23.500

63.360

826.93

42.62

84.95

95.04

29

870.00

25.000

63.360

854.28

48.14

95.96

107.36

1.50

30

900.00

25.460

63.360

881.39

53.91

107.46

120.23

0.46

31

930.00

25.460

63.360

908.48

59.69

118.99

133.12

0.00

130.51

146.02

0.00

32

960.00

25.460

63.360

935.56

65.48

33

990.00

25.460

63.360

962.65

71.26

142.04

158.91

0.00

34

1020.00

25.460

63.360

989.74

77.04

153.56

171.80

0.00

35

1050.00

25.460

63.360

1,016.82

82.82

165.09

184.70

0.00

1080.00

25.460

63.360

1,043.91

88.61

176.61

197.59

0.00

188.14

210.49

0.00

36 37

1110.00

25.460

63.360

1,071.00

94.39

38

1140.00

24.440

63.360

1,098.18

100.08

199.48

223.18

1.01

39

1170.00

23.240

63.36.0

1,125.62

105.52

210.32

235.31

1.20

A2-15

JX Nippon

on & Gas Exploration

40

1200.00

22.040

63.360

1,153.31

110.70

220.65

246.86

1.20

41

1230.00

20.840

63.360

1,181.23

115.62

230.45

257.83

1.20

42

1260.00

19.640

63.360

1,209.38

120.27

239.73

268.21

1.20

43

1290.00

18.440

63.360

1,237.73

124.66

248.48

277.99

1.20

44

1320.00

17.240

63.360

1,266.29

128.78

256.69

287.19

1.20

45

1350.00

16.040

63.360

1,295.03

132.64

264.37

295.78

1.20

46

1380.00

14.840

63.360

1,323.95

136.22

271.51

303.77

1.20

139.53

278.11

311.15

1.20

1410.00

13.640

63.360

1,353.03

48

1440.00

12.440

63.360

1,382.25

142.56

284.16

317.92

1.20

49

1470.00

11.240

63.360

1,411.61

145.32

289.67

324.08

1.20

50

1500.00

10;.040

63.360

1,441.10

147.81

294.62

329.62

1.20

51

1530.00

8.840

63.360

1,470.69

150.02

299.02

334.54

1.20

52

1560.00

7.640

63.360

1,500.38

151.95

302.86

338.84

1.20

53

1590.00

6.440

63.360

1,530.15

153.60

306.15

342.52

1.20

54

1620.00

5.240

63.360

1,560.00

154.96

308.88

345.57

1.20

47

55

1650.00

4.040

63.360

1,589.90

156.05

311.05

348.00

1.20

56

1680.00

2.840

63.360

1,619.84

156.86

349.80

1.20

57

1710.00' •

1.640

63.360

1,649.82

157.39

312.66 313.71 ~ -

350.98

1.20

58

1740.00

0.440

63.360

1,679.81

157.63

314.20

351.52

1.20

59

1770.00

0.000

0.000

1,709.81

157.65

314.24

351.57

0.44

60

1800.00

0.000

0.000

1,739.81

157.65

314.24

351.57

0.00

61

1830.00

0.000

0.000

1,769.81

157.65

314.24

351.57

0.00

62

1860.00

0.000

0.000

1,799.81

157.65

314.24

351.57

0.00

63

1890.00

0.000

0.000

1,829.81

157.65

314.24

351.57

0.00

64

1920.00

0.000

0.000

1,859.81

157.65

314.24

351.57

0.00

65

1950.00

0.000

0.000

1,889.81

157.65

314.24

351.57

0.00

66

1980.00

0.000

0.000

1,919.81

157.65

314.24

351.57

0.00

67

2010.00

0.000

0.000

1,949.81

157.65

314.24

351.57

0.00

68

2040.00

0.000

0.000

1,979.81

157.65

314.24

351.57

0.00

69

2070.00

0.000

0.000

2,009.81

157.65

314.24

351.57

0.00

70

2100.00

0.000

0.000

2,039.81

157.65

314.24

351.57

0.00

71

2130.00

0.000

358.980

2,069.81

,157.65

314.24

35~.57

0.00

72 73 74 75 76 77 78 The dogleg severity is in degrees per 30 meters Rectangular coordinates given relative to well system reference point The vertical section origin is the wellhead The vertical section was computed along 194.98 degrees (true) The calculation method is Minimum Curvature

A2-16

\._J


[4] Job Outline Drilling

o.

Preparation / Guidelines 0.1. NK-28 and NK-38wells are in close proximity to the planned NK-67well path. Ensure wells are shut in prior to spud in, and remain shut in during drilling and completion operation. 0.2. 30"stovepipe was set before rig units installations. 0.3. Check drill logger and all instruments before spud in. 0.4. Prepare 50 KL Gel mud in accordance with mud program. 0.5. Make-up enough number of 5"DPstands for cementing and set back. 0.6. Make up the cement stinger and rack back. 0.7. Check recommended make up torque for all connections of drilling assembly.

1.

Drilling 26" Hole and set 20" Casing Drilling 1.1. Make up 26"rotary assembly as per BRA program. Ensure that all tubular are drifted, including DCs. 1.2. Drill 26"holesection to ±360 m MDBRTas follows: ~ Run TOTCOID~to make sure the angle is less than 1.0 deg before spud. ~ Run TOTCO/Drat first single down, every +/-90m, TD. ~ Depth will change depending on the length of casing and required sump hole. ~ Perform short trips every 180m. ~

Cuttings will be checkedby JX Geologistto confirm there are no sand formations around casing shoe depth.

1.3. Circulate the hole clean. Pump Hi-Vismud, if required. 1.4. POOH 26"rotary assembly to surface. 1.5. Run back 26"rotary assembly in the hole to check fill. 1.6. Circulate the hole clean and condition the mud. 1.7. POOH 26"rotary assembly. Casing run and Cementing 1.8. Rig up casing running equipments. 1.9. Run 20"casing in accordancewith casing running procedure. ~

Followingto casing running procedure and centralizer installation procedure. A2-17


>-

When the last joint of casing is landed on the table with the elevator, do not use slips for landing. Put 2" iron plate between elevator and rotary table, to check slack after WOCand to release elevator.

1.10. Run cement stinger assembly.

>- >-

Prepare special bowl and slips for running 5"DP. Ensure a 20" centralizer is attached on the 5" DP approx. 1 to 2m above the cement stinger.

>-

Ensure circulation through string before stinging into the 20" shoe.

-1.11. Carry out cementing as per program, POOH with stinger assembly.WOC. 1.12. Wait on cement until surface samples are firm.

>-

During WOC,roughly cut 30"casingby cutting torch and centralize 20"casing inside 30"casingwith iron plates. Make a final cut of 30"casing as per well head installation procedure.

>-

After WOC,slack offelevator by removing -2"iron plates to confirm the cement becomeshard. If 20"casingis stationary, 'make a final cut of 20"casing as per well head installation procedure.

1.13. Install 21-114"casing head, Weld 30"x 20" SOWwlbase plate casing head assembly. 1.14. Wait on cooldown to pressure test for welding portion and test with 580 psi from test port. 1.15. Nipple up 21-1I4"BOPstack and carry out BOP test as per JX instructions 1.16. Mix sufficient new KCL-Lignate mud as per mud program.

>2.

Change screens on the shaker in accordance with mud program.

Drilling 17-112"Hole and set 13-3/8"Casing Drilling 2.1. Install wear bushing 2.2. Make up 17-112"drilling assembly as per BHAprogram. 2.3.• "RIH 17-112"drilling assembly to the top of float shoe.

->>-

Take care when running both the bit and stabilizers through the BOPs Pick up sufficient additional 5" DP to drill entire hole section.

2.4. Tag cement and pressure test casing to __

psi.

2.5. Drill out cement and 20" shoe track, rat hole and 5m of new formation. 2.6. Pump 5KLof Hi-Vismud and circulate to clean up the well.

>-

Dress up around 20"shoewhile circulating.

2.7. Displace well to KCL-Lignate mud. A2-18


2.S. Perform shoe bond test as per JX instructions. ~ Pull back inside the 20" casing shoe. ~ Perform shoe bond test against the pipe rams. 2.9. Drill ahead 17-112"hole section to ±1,000 m MD BRT in accordance with Sperry-sun directional program as follows: ~ Adjust tool face to the desired direction by scribe line drawn on 5"HWDP. ~ Take long survey and check magnetic interference. Rig up GYRO,if required. ~ Kick offwith 3.0 /30m dog leg on an azimuth of 63.36°to ±25° inclination by ±S70 0

m MD BRT.Then drill tangent to section 'rn of±I,OOOm MD BRT. ~ MWD surveys to be taken at each connection to control build rat. ~ Record drilling parameters every stand (up, down and rotating weights, drilling and offbottom torque, pump pressure). ~ Perform short trips every 300 m. 2.10. Circulate to clean up the well. 2.11. POOH with 17-112"drilling assembly. 2.12. Make up wiper trip / reaming run assembly and RIH to TD. 2.13. Circulate to clean up the well and condition the mud. 2.14. POOH wiper trip assembly. 2.15. Retrieve wear bushing.

Casing run and Cementing 2.16.Rig up casing running equipment. 2.17.Run 13-3/S"casingin accordance with casing running procedure. ~

Following to casing running procedure and centralizer installation procedure.

2.1S.Carry but cementing in accordance with cementing program. 2.19. Flow check the annulus for 15minutes. 2.20. Pick up 21-114"BOP stack and set the 13-3/S"casing slips and slack offtension as per wellhead instruction. 2.21.Rig down cementing head and circulating lines. 2.22. Rough cut as per well head installation procedure and recover the excess string. 2.23. Nipple down 21-114"BOP stack. 2.24. Final cut and prepare the 13-3/S"casing as per wellhead installation procedures. 2.25. Nipple up 21-114"2K x 13-5/S"5K casing spool.Test with 3,000 psi from test port. 2.26. Nipple up 13-5/S"5K BOP stack. A2-19


~ Test choke and kill lines to 5000psi. ·2.27.Pressure test 13-5/8"5K BOPs and surface equipment as per JX instructions. ~ Make up and run the 13-3/8"combination test tool on 5" DP. ~

Open the casing spool side outlet valve and monitor for leaks during testing.

~ Test the BOP stack as per the test schedule. ~ Retrieve 13-3/8"combination test tool on 5" DP. 2.28.Install 13-3/8"wear bushing. 2.29.Mix sufficient new KCL-Lignatemud as per mud program. ~ 3.


Drilling 12-114"Hole and set 9-5/8"Casing Drilling 3.1. Make-up enough number of 5"DPstands. 3.2. Make up 12-1/4"drilling assembly as per BHApr,ogram. 3.3. RIH 12-114"drilling assembly to the top of float collar. ~ Take care when running both the bit and stabilizers through the BOPs 3.4. Tag cement and pressure test casing to __

psi.

3.5. Drill out cement, 13-3/8"collar and shoe track, rat hole and 5m of new formation. ~ Record drilling parameters. 3.6. Pump 5KLof Hi-Vismud and circulate to clean up the well. ~ Dress up around 13-3/8"shoewhile circulating. 3.7. Perform shoe bond test as per JX instructions. ~ Pull back inside the 13-3/8"casing shoe. ~ Perform shoe bond test against the pipe rams. 3.8. Displace well to new KCL-Lignatemud. 3.9. Drill ahead 12-114"hole section-to±1,660 m MD BRTin accordancewith Sperry-sun directional program as follows: ~ Drill tangent section to ±1,llOm MD BRT. ~ Drill Drop to section of TD ±1,660mMD BRT. ~ MWDsurvey to be taken at each connection. ~ Record drilling parameters every stand (up, down and rotating weights, drilling and offbottom torque, pump pressure). ~ Perform short trips every 300 m. 3.10. Circulate to clean up the well. A2-20


3.11. POOH with 12-114"drilling assembly. 3.12. Make up wiper trip /'reaming run assembly and RIH to TD. 3.13. Circulate to clean up the well and condition the mud. 3.14. POOH wiper trip assembly. 3.15. Retrieve wear bushing. Casing run and Cementing 3.16.Rig up casing running equipment. ~

Change pipe ram to 9-5/S".

3.17.Run 9-5/S"casingin accordance with casing running procedure. ~

Following to casing running procedure and centralizer installation procedure.

~

Fill casing with mud everyfive joints.

~ The casing tally should place 9-5/S"stick up ±lm above the rotary table and ensure no couplings are across the wellhead area. 3.1S.Carry out cementing in accordance with cementing program. 3.19. Flow check the annulus for 15minutes. 3.20. Set back 13-5/S"5KBOP stack and set the 9-5/S"casing slips and slack offtension as per wellhead instruction. 3.21.Rig down cementing head and circulating lines. 3.22.Rough cut as per well head installation procedure and recover the excess string. 3.23. Final cut and prepare the 9-5/S"casing as per wellhead installation procedures. 3.24. Nipple up 13-5/S"5K x 11"5K casing spool. Test with 3,000 psi from test port. 3.25. Nipple up 11"5Kx 13-5/S"5Ksub flange and 13-5/S"5K BOP stack. ~ Test choke and kill lines to 5000psi. 3;26.Pressure test 13-5/S"5K BOPs and surface equipment as per JX instructions. ~ Make up and run the 13-3/S"combination test tool on 4-112"DP. ~

Open the casing spool side outlet valve and monitor for leaks during testing.

~

Test the BOP stack as per the test schedule.

~ Retrieve 13-3/S"combination test tool on 4-112"DP. 3.27. Install 9-5/S"wear bushing. 3.2S.Mix sufficient new KCL-Lignate mud as per mud program. ~ 4.


Drilling S-1I2"Hole and set 5-112"Casing Drilling A2-21


4.1. Make up 8-112"drilling assembly as per BHA program. 4.2. RIH 8-112"drilling assembly to the top of float collar. ~

Take care when running both the bit and stabilizers through the BOPs

~ Pick up sufficient 5" DP to drill entire hole section. 4.3. Tag cement and pressure test casing to __

psi.

4.4. Drill out cement, 9-5/8" collar and shoe track, rat hole and 5m of new formation. ~ Record drilling parameters. '0."

4.5. Pump 5KL of Hi-Vis mud and circulate to clean up the well. ~

Dress up around 9-5/8"shoe while circulating.

4.6. Perform shoe bond test as per JX instructions. ~

Pull back inside the 9-5/8"casing shoe.

~

Perform shoe bond test against the pipe rams.

4.7. Displace well to KCL-Polymer mud. 4.8. Drill ahead 8-1/2"hole section to ±2,130 m MD BRT in accordance with Sperry-sun directional program as follows: ~

Drill drop section to ± 1,750m until 0 degree.

~

Drill vertical hole to section TD of ±2,130m MD BRT.

~ Actual TD will be confirmed by the Well Site Geologist. ~ MWD survey to be taken at each connection. ~ Record drilling parameters every stand (up, down and rotating weights, drilling and offbottom torque, pump pressure). ~

Perform short trips every 300 m.

4.9. Circulate to clean up the well. 4.10. POOH with 8-112"drilling assembly to 9-5/8" shoe. 4.11.' Run back to bottom. 4.12. Circulate to clean up the well and condition the mud. 4.13. POOH with 8-112"drilling assembly. Logging 4.14. Open hole logging. ~

The following open hole logs required: DLL-FWS-GR,GRN, CDL-GR,XRMI

~ Run a reaming assembly and ream down prior to xxx survey, in order to reduce the' stacking risk. 4.15. Make up wiper trip / reaming run assembly and RIH to TD. 4.16. Circulate to clean up the well and condition the mud. A2-22


4.17. POOH with wiper trip assembly. 4.18. Retrieve wear bushing. Casing run and Cementing 4.19. Rig up Weatherford casing running equipments. ~

Change pipe ram to 5-1/2".

4.20.Run 5-1I2"casingin accordance with casing running procedure. ~

Followingto casing running procedure and centralizer installation procedure.

~

Fill casing with mud every five joints.

»

The casing tally should place 5-112"stick up ±lmabove the rotary table and ensure no couplings are across the wellhead area.

4.21. Carry out cementing in accordance with cementing program. 4.22. Flow check the annulus for 15minutes. 4.23. Pick up 13-5/8"5KBOP stack and set the 5-112"casing slips and slack offtension as per wellhead instruction. 4.24.Rig down cementing head and circulating lines. 4.25. Rough cut as per well-head installation procedure and recover the excess string. 4.26. Nipple down 13-5/8"5KBOP stack. 4.27. Final cut and prepare the 5-1/2"casing as per wellhead installation procedures. 4.28. Nipple up 11" 5K x 7-1116"5K tubing spool. Test with__

psi from test port.

4.29. Nipple up 7-1116"5K x 7-1116"10K sub flange and 7-1116"10K BOP stack. ~ Test choke and kill lines to 5000psi. 4.30. Pressure test 7-1116"10K BOPs and surface equipment as per JX instructions. ~ Make up and run the 5-112"combination test tool on 5" DP. ~

Open the tubing spool side outlet valve and monitor for leaks during testing.

~ Test the BOP stack as per the test schedule. ~ Retrieve 5-112"combination test tool on 5" DP. 4.31. Install 5-112"wear bushing. 4.32. Lay down excess 5"DP. 5.

Clean up the well. Drill out cement 5.1. Make-up enough number of 2-7/8"HWDP and 2-7/8"DP stands. 5.2. Make up 4-3/4"bit assembly as per BHAprogram. 5.3. RIH 4-3/4"bit assembly to the top of float collar. A2-23

JX .Nippon Oil & Gas Ex.ploration

~ Take care when running the bit through the BOPs ~ Pick up sufficient 2-7/8" DP to drill entire hole section. 5.4. Tag cement and pressure test casing to __

psi.

5.5. Drill out cement to 5-112"collar. ~ _Record drilling parameters. 5.6. Pump 5KL of Hi-Vismud and circulate to clean up the well. 5.7. POOH with 4-3/4" bit assembly. 5.8. Make up 5-1/2" scraper assembly as per BHAprogram. 5.9. RIH 5-112"scraper assembly to the top of float collar. ~

Take care when running both the bit and scraper through the BOPs

5.10. Circulate to clean up the well. 5.11. POOH with 5-112"scraper assembly. Logging 5.12. Cased hole logging. ~ The followingcased hole logs required: RCBL-GL

[5].Run Completion and Flow test 5.13. Rig up Weatherford tubing running equipments. 5.14. Make up 5-112"SC-2 packer assembly as per BHI instructions. ~ Use water to make sure it is clear and no debris inside assembly. 5.15. Rig down BJ tubing running equipments. 5.16. RIH 5-1/2" SC-2 packer assembly with 2-7/8"DP. ~

Before RIH inspect packer for damage to slip or element and re-check all-shear pms,

~ Running trip tank during RIH to check hole conditions. ~ Record pick up weight and slack offweight at packer setting depth. 5.17. Set 5-112"SC-2 packer assembly at __ m as per BRI instructions. 5.18. Circulate to clean up the well. 5.19. POOH with packer setting tool. 5.20. Retrieve wear bushing. 5.21. Rig up BJ tubing running equipments. 5.22. Make up and RIH EBH-22 anchor seal assembly while picking up 2.;3/8" VAMTOP tubing. A2-24


~

Following to completion tally and profile.

~ Running trip tank during RIH to check hole conditions. ~ Record pick up weight and slack offweight at packer setting depth. 5.23. Space out, Make up tubing hanger with landing joint, and Land on. ~ ...Record final weight with out hook. 5.24. Rig down BJ tubing running equipments. 5.25. Screw in tie down volts and pressure test annuals. ~ Pressure up annulus to 1,000psi to check the leakage of seal assembly and tubing connections. 5.26. Lay down landing joint and install H-2 back pressure valve. 5.27. Carry out pressure test for hanger with 1,000 psi. 5.28. Nipple down 7-1/16" lOKBOP stack. 5.29. Nipple up Xmas tree and pressure test to 3,000 psi. 5.30. Lay down 2-7/8" HWDPand DP. 5.31. Rig up coiled tubing and fabricate surface line as per Halliburton instructions. ~

~

5.32. RIH 1.25"coiled tubing while pumping fresh water. (KCL_%) 5.33. Circulate to clean up the well and displace fresh water. (KCL_o/c) 5.34. N2 lift at _m

and flowtest as per JX instructions.

5.35. POOH with 1.25"coiledtubing and Rig down. 5.36. Rig down all and demobilizations

[6]

Detailed job Instruction

BHAList DRILLING DRL-l:

Spudding 26"Bit + Bit sub + 8" Float sub + 8" Saver sub + 8" NMDC+ 8" Saver sub + 8" DC x 6 +XlO

DRL-2: Drill 26" Hole 26"Bit + 26"Stabilizer + B/S+ 18"Float sub + 8" Saver sub + 8" NMDC+ 8" Saver sub + 8" DC x 6 + XlO A2-25


DRL-3:

Kick-offand drill 17-1/2"hole 17-1/2"Bit + 9-5/8"Sperry-drill motor (17-114" STB, 0.78° adj bent, Lobe=617, Stage=5.0) + 17-1I4"Stab + XlO (7-5/8"Reg Pin x 6-5/8"Reg Box) + 8"F/S + 8"HOC w/Pulsar & PCDC + 8"SNMDC + XlO (6-5/8"RegPin x NC50 box) + XlO (NC50 Pin x 4"IF Box) + 6-1I2"DCx 12 + XlO + 5"HWDP x 12 + 6-3/4"Jar + 5"HWDP x 2

DRL-4: Reaming 17-112"Hole 17-1/2"Bit + 9-5/8"Sperry-drill motor (17-114" STB, 0.00° adj bent, Lobe=617, Stage=5.0) + 17-1/4"Stab + XlO (7-5/8"Reg Pin x 6-5/8"Reg Box) + 8"F/S + XlO (6-5/8"RegPin x NC50 box) + XlO (NC50 Pin x 4"IF Box) + 6-1I2"DCx 12 + XlO (4"IF ~ Pin x NC50 Box) + 5"HWDP x 12 + 6-3/4"Jar + 5"HWDP x 2

,..

DRL-5: Drill 12-1/4"hole 12-1I4"Bit + 8"Sperry-drill motor (12-1I4"STB,0.78° adj bent, Lobe=617,Stage=4.0) + 12-1/4"Stab + 8"F/S + 8"HOC w/Pulsar & PCDC + 8-1I2"SNMDC+ XlO (6-5/8"RegPin x NC50 box) + XlO (NC50 Pin x 4"IF Box) + 6-1/2"DC x 12 + XlO (4"IF Pin x NC50 Box) + 5"HWDP x 12 + 6-3/4"Jar +5"HWDP x 2 DRL-6: Reaming 12-114"hole 12-1I4"Bit + 8"Sperry-drill motor (12-1I8"STB,0.0° adj bent, Lobe=617,Stage=4.0) + 12-1I4"Stab + 8"F/S + XlO (6-5/8"RegPin x NC50 box) + XlO (NC50 Pin x 4"IF Box) + 6-1I2"DCx 12 + XlO (4"IF Pin x NC50 Box) + 5"HWDP x 12 + 6-3/4"Jar +5"HWDP x 2 DRL-7:

"-"

Drill 8-1/2"hole 8-1I2"Bit + 7"GeoForce motor (8-1I4"STB, O.Ooadjbent, Lobe=617, Stage=4.5) + 6-3/4"Float sub + 8-1I2"Stab + 6-3/4"HOC w/pulsar & PCDC + 6-3/4" SNMDC + 8-1I2"Stab + XlO (NC50 Pin x 4"IF Box) + 6-112"DC x 12 + XlO (4"IF Pin x NC50 box) + 5"HWDPx 12 + 6-3/4"Jar + 5"HWDP x 2

DRL-8: Reaming 8-112"Hole 8-1I2"Bit+ Bit sub + 6-3/4" Float Sub + 8-1I4"STSTB + 6-3/4"DC+ 8"Stab + 6-1I2"DC x 11+ XlO (4" IF Pin x NC50 box) + 5"HWDP x 12 + 6-3/4"Jar + 5"HWDP x 2

A2-26


COMPLETION CMP-1 : 4-3/4" bit assembly 4-3/4"Rock bit (open nozzle) + 4-1I2"Junk sub + BIB + 3-3/4"DC (IF) x 12 + 2-7/8"DP (IF) CMP-2 : 5-112"scraper assembly 4-3/4"Bit (open nozzle) + 5-1I2"Scraper + 4;1I2"Junk sub + XJO + XJO + 3-3/4"DC x 12

A2-27


Bit Program

TSK IADe

s= z: C:

124

Type (lADO 12- )

Z-series Bearing Center Jet

FORMATIONS Soft with IQw compteElltlVestrenJtb. (soft

6alce, clays, rod bed." $&.1t., uneoXl801idat.od ea ads)

DES/GN SPEC/FlCA nONS 26" (UO ..... )

Bit Size

Sialed Roller

aear Inl Type Journll Of het

(•• )

0' Gaie

Nu.ber

BeariAI

33

Anil e

'l4.4

3 / a

Rows/Inner Row.

Iv.be, of Teeth

---------------------------------------------------------------t3S

Bit Connectlo.

Type

1-S/a- ~el

GeNERAL OPBRA TION PA/lAMJ;JTe/M 81 t Size

lei,ht Lb,

%6" (660.4 •• )

on BIt I

1."Uh

20 - 65

ToftS. Rotary Speed(rpa)

9 - 29 80 -

150

CUTTING ST1WCTURB This type features and width for drilling

widely

_ott

;spaced, hll'ge tooth Corm.tione.

Large eone offset promotes gouging- and scraping to increase ROP.

heigh.t

actiou

Hardfaced a.feu are shown in loft figuro. (yellow portion)

Note: The gace surface and. the backface of innc.r teesh are also hardfaced.

A2-28

JX Nippon Oil It: Ga.s Explora.tion

z

'$

a

o E Q.

U

c: 00

« co -

N

~~O

~NlI6lm

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.;:011-

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A2-29

JX Nippon Oil & Gas Ex.ploration

17·1/2"

(444rnm)

EBXT1GRC

A2-30

Gc JX Nippon

.

12·1/4"

-

(311mm)

EQHC1GRC

PRODUCT ~:\A-""'''n.~ ·IAOCC-Odf

Oil & Ga.sExploration

111\V 4

-~

83_44 30-447

.QmerJmd) :

so

813

6-... (API :Re,,)

U?s. ·.3Kg,) 53 3. 5t'J6463

A2-31


8-1/2"

(216mmJ

QHC1GR

PRODUCTSPECFICA 17\V

t.oOOl·u~ •

~~~_~to;p:mjde~~\"e

!

, !3CDQC.a!-~ROP. -~arl:L:Se! ':5Df' ~:lD

~~dy:m __

~~m~

~"' ........'" _ .. ~

tl";

P:~ teeth fk.addied~'

. Vb arl:adit

m:idt:m:md,~

-.._

seal'C!d:!:»~_~··~ CO!::xll: pr;!5SDIl'M4:Ja·'O!~

be!i~om~~

edps

of_l\m

f!lehigben

sa!lll~:U.is

A2-32

~


Casing & Centralizer Program 2015/07/10

NK-67 20" Casing CentralizerPlan

Centralizer Spacing

=

12m (1 pc I it)

2" Iron Plate Bushing(W/ford)

XXm

Lube Seal

No. XX

Centralizer

Lube Seal

(Last centralizer)

No.5 Centralizer

Lube Seal

No.4

Lube Seal

Centralizer

WeidA (Tack Weld btm of conn.)

Centralizer

Centralizer

WeidA (Tack Weld btm of conn.)

Centralizer wI stop collar tack welded

A2-33


2015/07/10

NK-67 13-3/8" Casing Centralizer Plan

Centralizer Spacing No

No. XXXj

Centralizer ((

Lube Seal

»

II

~

No. XXjt

((

Lube Seal

Over the coupling (Last centralizer)

No.XXXj

""

Ir

Over the coupling

t 1 pc 12 its (24m)

No. XXjt

Lube Seal No. XX it

«

Lube Seal

No. xx ::::=

((

Lube Seal

))

II

Over the coupling

jr

~ No.7 [t 1/ ))

Ir

Over the coupling

No. Git Lube Seal ((

»

Over the coupling

»

Over the coupling

»

Over the coupling

II

No.5 it Lube Seal ((

lr

No.4 jt WeidA ((

(Tack Weld btm of conn.)

.11

No.3 it

. _j_ WeidA

1.5m

WeidA

1.5m

((

-r-

---r_j_

Weld A

1.5m

(Tack Weld btm of coim.)

)~

Centralizer with stop collar

lFloat cOlla1

_j_ (Tack Weld btm of conn.)

1 pc I jt

((

»

Centralizer with stop collar·

))


»


No.2 it ((

-rNO.1 it ((

WeidA

[

Shoe

A2-34

1

(12m)


NK-67 9-5/8" Casing Centralizer

2015/07/10

Plan

Centralizer Spacing

Thread compound

No. XX JT No Centralizer Lube Seal No. XX JT ...==

~

~ No. XX JT

Cased

Lube Seal

ole

No. XX JT

((

Lube Seal

II

»

(Last centralizer)

No. XX JT

== ~

Over the coupling Open hole

,.;

No. XX JT

1 pc 12 jts (24m)

Lube Seal ...==

No. XX JT

~

~ No.7 JT

Top of XX (formation)

))

Lube Seal

Over the coupling

---+---

" NO.6 JT

((

Lube Seal

II

Over the coupling 1 pc 1 jt (12 m)

No.5 JT Over the coupling II

«

Lube Seal

No.4JT Over the coupling WeidA (Tack Weld btm of conn.) No.3 JT

WeidA

.

WeidA

__L

(Tack Weld btm of conn·t5

.....,-

))

((

.....,-

1.5 m


[Float cOllarJ

m

):

((


No.2 JT

__l_ (C

.....,-

1.5 m WeidA (Tack Weld btm of conn.)

Centraliz.er with stop collar

»


No.1 JT

1·r

«

WeidA

»

~

A2-35

Gc JX Nippon Oil & Gas Exploration

2015/07/10

NK-67 5-1/2" Casing Centralizer Plan

Centralizer Spacing

Thread compound lNo.XX JT

No Centralizer Lube Seal No. XX JT

=~

k""

No.XX JT

Cased hole

Lube Seal No. XX JT ((

Lube Seal

))

.,,:==

No. XX JT

~

Over the coupling (Lastcentralizer)

Open hole

~

No.XX JT

1 pc 12 jts (24m)

Lube Seal No. XX JT

»

((

Lube Seal

__

+-_T_o_p of XX (formation)

Over the coupling

No.XX JT ,::=

~

No.6 JT

V

((

Lube Seal

Over the coupling 1 pc 1 jt (12 m)

No.5 JT Over the coupling ((

Lube Seal

No.4 JT Over the coupling

WeidA (TackWeld btm of conn.)

((

II

))

No.3 JT 1.5 m

J

((

-r

[Float cOllarJ

WeidA _j_ (TackWeld btm of conn·t5 m

-r _j_ Weld A 1.5 m (TackWeld btm of conn.)


J

((


No.2 JT ((

'/


);


-r No.1JT ((

WeidA

~

A2-36


Mud logging plan

Monitoring

>>>>>>>~

data from 360m:

Measuring

for every 1m or 1min

WHO WOB SPP TORQUE PIT LEVEL HOOK HEIGHT TOTAL GAS ROP

..

Electrical logging Open Hole Logging (8 1/2"Hole Only) ~.. >- GR-FWS-DLL

>>-

GRN

~

XRMI

GR-CDL

Cased Hole Logging (5-1/2" Casing Only)

>-

RBT-GR-CC

Perforation

A2-37


[7] Others Completion program, Wellhead specification

A2-38


Completion program Design of CompJetton (or NK-67 CONFIDENTIAL ~l~Uf1I

·~.~r.

IIIIIla'

£,111

~dCiq(;

t"'''''' r OhP

~Ptft.W,.

OP! .iiJ P 1 ">051 JI' tz<.t< I&.. a ?'J 111" '
31 Co!Vc, ~ ltlOf , \tP l?'" ~

A.,NAW filAld VDt

laHT( IeooM lVO)

A2-39

~

c;

J

)Ii

'" sa

lfI.I lIS

Ot-I 'GG3"s

061

I~~C."W '21..<. CPJ

'~·sc.

t! ~"'~.

.!S3

1"~~"

IBHP(twum

La.. ,PrO
11~

r

,Jd

PJ P.t

'l7 '" 1I2H··~ C

1'''' LlI't 1tl"O C

J

2;l4t1. IF

Z3 _~


ltem

Material

10

Number TBD

Leg.ac:y Humber

T80

Oescription PHL Hydraulic-Set Perma..

Qty

UOM

2

EA

lach® Refrievable Pac Bt,5 1/2 in 13·17 tWit We~ht Range, 4.700 in. Max 00. 1.917 in. Min 10. 41XX LOW AllOY STEEL Matt. 80000 psi Min Yield. Hydrogenated nitrile rubber Element Matt, Fluorocarbon rubber a·Rin.g I

Matt, 2'318-4.6 VAMTOP .Box x 2 318-4.60 VAMTOP Pin, 325 Oeg. F, H2S Service, 7500; 7500;5000-psi Pressure Rating.

_._

20

T80

TaO

HaUiburton® Durasleeve® Sliding. S e Door® Crrculating and Production Oevice, 2.375 in., 46.01 in. leng1h, 23184.60 VAMTOP BOX·P·IN. Connection, X. 41XX LAS Matt. 1.875 in. Seat Bore 10Min, 3.220 in. Max 00. 41XX lAS Closing Sleeve Matt.

2

EA

30

T80

T80

B.last Nip.pte. eN, 2 318 in.• 2.138 in. Max 00.1.907 in. Min 10, 121.0 in. Length,

6

EA

1

EA

3

EA

41XX lOW ALLOY STEEL Matl, 80000 psi Mjn Yield, H.2S S'erv·ce. 2 318-4.60 VAMTOP Box x Pin. 40

101753384

12PNZ2753 5-E

No-Go Seal Unit Lecator, 2.750 in. Seal Bore tt)..Min. 2 318-4.60' VAMTOP Box x 2 3/8... 4.60 API-NU Pin, 3.07 in. Max 00.1.875 in. Min..ID. 14.10 in. length. 41XX lOW AllOY STEEL Matt, 110000 psi Min

Yield. 50

100014761

212MSN275 OO-A

MSN Molded Nitrile Seal Unit, 1.920 in. Min 10. 2.750 in. Seal Bore ,IO-Min. 13.18 in. Length, 12.00 in. Mak,e-up Length. 41XX LOW..ALLOY STEEL Malt, Nitrite rubber Seal Matt. Molded. 2 318API-NU Box x 2

3/8-4.60 API-NU P x . 40-215 Oeg. F. Std SaNiee. 10000"psi Pressure Rating.

A2-40


ftem 60

Matedat Number 101044056

70

101782768

Description

Legacy Number 212M320

12VTA5502 7·.Z

UOM

Q

Wire line Re-entry Guide, 2 318 APJ..NUE Box. 1.920 In. Min 10; 2.710 in. Max 00, 5.00 in. length, AllOY Matt~80000 psi Min Yiefd, .. H2S Service

1

EA

vt« Versa-Trieve(R)

1

EA

Sottom Sub for Versa-Trieve Packet, 4 3/16-12 UNS-2A Pin x 2 3/&-.4.60 VAMTOP Pin, 4.470 in. Max 00, 2.750 in. Min 1,0 28.04 in. length, AHoy MaU. 80000 psi Min Yield. H2S Service.

1

EA

01is® XN® landing Nipple with ,Boltom No-.Go. 1.875 in .• 2.707 in. Max 00. 1.791 in.

1

EA

1

EA

Retrievable Sand Control Packer, 5112 in., 14- 7 Jbltt Weight Range. 2.750 in Seal Bore 'Oo-Min, 41XX lOW AllOY ..sTEEL Matl. 110000 psi MlO Yield. Hydrogenated nitrile rubber Element Mat!, 4

3/16 ..12 UNS-2B 4.670 in. Max 00.2.750 in. Min IDf..'73~68in. length. 35116-6 STUB AC-LH Type Latch, 275 I

•

Oeg. F.

80

'reo

leo

1

90

TBD

TBD

Min No-Go

10. 16.69 in.

L'ength. 41XX LAS Matl.80000 .psiMin Yield. H2S Service, 2 318-4.60 VAMTOP Box x Pin. 10200 psi Pressure Rating. 100

TBD

TBD

Muleshoe Guide. 2. 970 in. Max 00, 1:947 in. Min 10, 6.00 in. Length. 41XX low Alloy Steel MatJ, 80000 psi Min Yield, 2 3/8-4.60 VAMTOP Box. H2S Service.

A2-41


Wellhead Specification

.fi9?. ?

953

A2-42

JX Nippon OilBr Gas Exploration

Appendix 3

Industrial Measurement and Process Automation ,

CONTENTS

GIAPTER ~,

1

Introduction

1.2 1.3

P r inc i pie 0 f Op era t ion Veloci ty Profi l e Effects

1.4

Si gna 1 Process

1.5

Ins

1.6

Factors Influencing F 1owme t e r

2. 1

»=.

t

a I 1 a t ion

Industrial

CHAPTER 2

3

I I-

3

•• ~. • • . • • • • . • • • · • • • • • · • • • I II 1•••••••.••.••••.•••••••

5

. .. .. . . . . .. . .. . . .. "

1.1

1.7

I 1-

ELECTROMAGNETIC FLOWMETERS

. I I - 21

Re qui r erne n t s Choice ,

of

an Electromagnetic . I I - 23

PLATE FLOW MEASUREMENT ············· ·

2.2 2.3

Or if ice

2.4

Dis c h a r g e Co e f f i c i en t s

2.5

Installation

2.6

Co n c 1u s ion

Pla t e s and

I I - 26

.•••..••.•••••.•.•..••••

Notat ion Introduction

Pressure

and Other

0

fOr

I 1- 29

•••.•••.•.••••

I I- 29 .. ·· .. ·· ······ ····· .. · · · . I 1- 29 I 1- 33 Tapp i ngs •••.••.•••• i f ice

Effects

I I - 37

P I ate s •.•.•.•

I I- 41

••..••••••••••••• iii

•

..

•

•

•

iii

•

•

•

•

•

•

•

•

•

•

I I- 45

OTHER FLOW MEASURING DEVICES ••.•.••••.•••••.

3.1

Introduct

ion

3.2

Positive

Displacement

3.3

Tu r bin e F 1 owrne t e r s

3 •4

U I t r a son i c F 1owrne t e r s

3•5

Va ria b 1e Ar e a F 1owme t e r s

3.6

Vortex

Shedding

I 1- 42

. I 1- 43

Acknowl edgemen t s CHAPTER 3

9

I I- 12

i ng ••••••••••••••••••••••.•••..••

Applications

ORIFICE

.

I 1- 45

· ••• Flowmeters

I I -:-45

.••••••••••••••

~ • . • . • • • • • . • .. • .. • • • • • • • • I I- 47

Flowmeters

I I -1

'.............

I 1- 48

.••••• .

._ .•••.....•••••.••..

I 1- 61

I 1- 63

CHAPTER 4.1 4.2

4

TEMPERATURE

4.4 4.5

CHAPTER 5.1 5•2

..•...•....•.....•.••

The Concept of Temperature and the Thermodynami ca 1 Sea 1 e .............•............ The International Practical Temperature Scale (IPTS)

4.3

MEASUREMENT

.......•

11

•••••••

tII

••••••

•••••••••••••

11- 65 I I - 65

I I- 66

Dissemination of the Temperature Scale . I I - 68 Types of Thermometer I I - 68 Installation and Use of Immersion Thermometers. II- 80 5 PRESSURE MEASUREMENT ......••..•....•.....•.. Introduction ....•..............................

II- 85

Ma n orne t e r •.•.•••••.•

I I - 87

~• . . . • • • . • • • • • • • • • • . . . • • • • •

De a d We i gh t Te s t e r •.••••••••••••••••••.•••••••• 5 • 4 Bo u rdon Tu be s , Ca p sII I esan d Be 1 1ow s ......•..... 5.5 Pressure Transducers . 5.6 Capacitance Type Press~re Transducer . 5 • 7 Re I u c t i ve Ty peP res sIIreT ran sdu ce r ••••••••••••• 5.8 Force Balance Pressure Transducer 5.9 Piezoelectric Pressure Transducer ..........•... 5 • lOS tr a i n Ga ug e Pre s sur e T ran sduce r ••••••••••••••• 5.11 Other Pressure Measuring Methods and

5 •3

Transducers

...•..•......•..•.............•..•..

I I - 85

I I - 88 I I - 89

II- 92 I I - 93 I I - 94 I I - 95

I I - 95 I 1- 96 I I - 98

GIAPTER 6 L I QU ID LEVEL NIEASUREMENT .••.•...•... . 11-101 6.1 Introduction ...•..•.•........•.....•......•..•. 11-101 6.2 Methods of Level Measurement . 11-101 6 • 3 S unma r y •••••••••••••••••••••••••••••••••.•• •••• 11-112 GIAPTER 7.1

1.2 1.3

7

CONTROL VALVES AND ACTUATORS

•••

~ •.••••••••••

11-115

Introduction .................•................. 11-115 The Restricting Element ..•..................... 11-116 Actuators .. . . .. .. . . . . . .. .. ... . 11-123

.... .... . ..... .

. . .

.............................

GIAPTER 8

GAS CHRCMATOGRAPHY

CHAPTER 9

TELEMETRY APPLICATIONS

11-2

..•....•..•..•....•...

11-133 11-139

Chapter

1

ELECTROMAGNETIC FLOWMETERS

1.1

Introduction The e lec t romag ne ti c flowmeter was developed for measuring the flow rate of fluids in installations where the more common methods of measurement were unsatisfactory. Its principal feature is that it does not present any obstruction to the flow of fluid and provided that the liquid is an electrolyte, it is relatively insensitive to changes in fluid density, viscosity and the flow profile. It also has an essentially linear response and is particularly suitable for measuring the flow of aggressive acids and alkalis as weI I as slurries wit coarse or fine suspended materials. Recent general information regarding the usage or application of the various methods ·of flow meaaurement in t e process industries suggests the breakdown shown in Fig.I.I.

Miscellaneous

(H%)

~/

_ Electromagnetic-r Flo\lllleters (9%)

Vortex Flo1o'1lleters

'\

Variable Area Flo"i.lmeters

(8%)

1.1

(2%)

Turbine Positive Flo1Jll1eters (5%) Displacement. Flowmeters

Fig.

Ultrasonic Fiololllleters (1j %)

(6%)

Relative usage of the prinCipal types of flowmeters

It should be emphasised that this information is very approximate because the method of reporting varies not only from one industry to another but also from country to country. 11-3

Also,

the understanding

definition indications

of process are

of which

industries

are

is vague.

However

the present

purpose.

industries

sufficie~t

for

included

the broad

the orifice phate in combination with a differential pressure transmitter in the field of flow measurement. This technique has a very long history starting with the work of Bernoulli published in 1738 on which the hydraulic equations for differential pressure meters are based. In 1797, Venturi described his basic work on the principles of the Venturi tube. However nearly a century was to elapse before Herschel developed a commercial venturi tube for measuring large volumes of flowing fluid. The o r i f ice p la te ernerged as the··p rima rye 1ernen t duri ng the fir s t decade of this century, and since then a vast amount of operational experience and performance data has been accumulated. On the other hand, although Faraday recognised that his law of magnetic induction applied not only to metallic conductors, but also to conductive fluids, his attempts in 1832 to measure the flow of the River Thames at Westminster Bridge by observing the voltage developed between two large plate electrodes as a result of the water flowing through the vertical Gomponent of the earth's magnetic field were unsuccessful. Wool aston claimed success in 1881 when he made.a simi lar experiment using a telegraph cable that had recently been laid across the English Channel. The f.irst experiments to investigate the effect of a transverse field on the fluid flowing in a circular pipe were reported by Williams in 1930, but apparently his interest was academic and he did not recognise the extent to which the concept could be exploited for practical measurements. It was in the medical field that the first practical designs were evolved, from 1936 onward, principally by Kolin, who identified many of the features which are to be found in modern electromagnetic flowmeters. Subsequent researchers in this field have made important contributions to the design and method of operation of these flowmeters and Wyatt and his colleagues at Nuffield College, Oxford, ·have made very detailed studies of many of the problems which arise in applying electromagnetic flowmeters, Th ere

are rnan y goo d rea son s for the dom ina nee

in the

11-4

0f

~J

particularly The

industrial

originated needed The

in the medical

a means

success

measurements

and

flowmeters,

theoretical

the

of some

of

the technique

starting aspects

about

period, of

the

appears

the dredging

flow

very

the subsequent

the same

flowmeters

where

for measuring

practical

During

of these

in the Netherlands

to the application of

use

field. industry

of sand/water

rudimentary to other

evolution

to have slurries.

equipment difficult

led flow

of a commercial

range

1955. several

flowmeter

workers

wer.e studying

performance.

For

the

exrunple,

with a uniform magnetic field to axis~etric flow velocity profiles, and Shercliff studied various applications associated with nuclear energy, including the measurement of the flow of liquid sodium. His theoretical studies and other work are collected in his book, which still provides a standard reference on the subject.

Thurlemann

1.2

I~

determined

Principle

the response

of a flowmeter

of Operation

Electromagnetic flowmeters comprise two basic parts, namely the flowtube or primary element which provides the means -of transducing the flow into an emf and the transmitter which converts this emf into a signal suitable for transmission over longer distances such as a proportional dc current in the range 4 to 20 rnA, a frequency in the range 0 to 10 kHz, or a pulse, in which case each pulse represents a predetermined volume of fluid.

Electrode

Flanged Metal Tube

Fig.

1. 2

E sse n t i a I c omp 0 n en t

electromagnetic 11-5

S 0 fan

flowmeter

The

essential

components

of a practical

electromagnetic

Fig. 1•2 • Th e me ta I tub e , f ab ric ate d from non-magnetic material such as stainless steel and fitted with flanges, provides the essential mechanical strength for the unit. It is lined with ptfe, polyurethane or other insulating material to minimise the short circuiting or diversion of ~he relatively small flow signal to the metal tube. The transverse magnetic field is generated by a pair of coils located on opposite sides of the tube (the core that completes the magnetic circuit is not shown), and the emf induced by movement of the fluid through the magnetic field is detected by a pair of electrodes located diametrically opposite each other with their axis perpendicular to both the magnetic field and the axes of the tube. The electrodes are usually fabricated in non-magnetic stainless steel, although other alloys such as Monel and Hastel loy, or those based on platinum, titanium, or tantalum are s ome t imes used. The kinetics of the interface between the metal electrode and the fluid are not only complex but also variable and unpredictable. The only practical method of reducing the effect of these spurious signals is to measure the change in interelectrode emf resulting from a known change in the magnetic field strength; in other words, to generate a flow measurement signal that is proportional to the flow emf divided by the magnetic field strength. The simplest form of excitation is to use the mains supply to energise the coils of the electromagnet, in which case the flow signal is an alternating emf of the same frequency and in phase with the magnetic flux. flow tub ear

Thus,

e shown

the induced emf is e

where

in

=

B.d.v.sin

=

mean flux angular frequency diameter of the flowtube

B

wt d

wt

11-6

+

Kw.B.cos

wt

~,I

v and The magnetic

K

mean

velocity

of

fluid

constant

first

term

flux.

The

is flow second

dependent term

and

is known

in phase as the

with

the

transformer

respect to the flow Signal, but is also independent of the flow rate. It arises from the fact that the leads to the measuring circuit combined with the effective current path through the fluid form ~ complete loop that is cut by the alternating flux, as shown in Fig. 1.3. signal

and

is not only

in phase

quadrature

with

-. Magnetic • ~.. flux

Area giving rise to transformer signal

Fig.

1.3

Source of the transformer

effect

signal

Although careful attention to positioning the leads can reduce this signal appreciably, it is still necessary to arrange the measurement circuits so that this unwanted component is rejected. However, the phase of the flux within the tube compared with that produced by the coils and the associated laminated yoke is modified by eddy currents in the metal tube and a Itho ugh the e f f ec tis rei at ivel y sma II, itis not con s tan t because changes of temperature change the conductivity of the metal and hence the magnitude of the eddy currents whilst variations of frequency change the mutual coupling, with the result that there is a variable zero error. The wave forms for this type of excitation are shown in Fig.l.4, with the errors due to changes in mains frequency and tempera~ure exagerated. For a typical flowtube 100 mm diameter 11-7

the f)ux 1 mV

density

for a mean

would

be 0.01

velocity

Tesla

and

the

flow

signal

about

of 1 m/s.

Mains

Voltage

~~--~~----~------~----~

Mains

Current

Magnetic Flux 0.01 Tesla Flow . Signal!

4-~~--~~:~~~~~+-~~~

1 mV

Fig.

1.4

Waveforms for an electromagnetic with sinusoidal excitation

flowmeter

Referring again to the transformer signal induced by imperfect location of the signal leads, this is proportional to the projected area cut by the flux and the rate at which the flux density changes with time. If the excitation is 50 Hz, the flux 0.01 Tesla and the projected area is 3 mm2 then this transformer signal would be approximately 10 uV. This represents 1% of the flow signal that would be developed in a typical electromagnetic flowmeter system. Since the general accuracy of these systems is usually better than 1 %, the importance of restricting this error by stable mechanical construction is apparent, although the signal conditioning circuits can ease this requirement. One possibly unexpected aspect of flowtube design arises from the fact that the flow signal is a function of the total flux, rather than the flux density that is cut by the flowing fluid. Consequently, if the same measuring circuit is to be used for a range of flowtubes, then one of the prinCipal problems in designing the small flowtubes is how to concentrate the necessary total flux into the test section, whilst for the

1I-8

large sizes, in the coils total

flux,

the problem is that of minimising the copper loss which, although they need only to produce the same must,

of necessity,-

extend

over

a much

larger

area.

Velocity Profile Effects It is seldom possible to arrange the installation of a flowmeter so that the flow profile is axisymmetric. There is usually a valve, bend, or junction upstream of the flowmeter which di~torts the flow profile. Extensive theoretical studies have been made to determine the relationship between the signal generated in an electromagnetic flowmeter, the velocity profile, the shape of the magnetic field and the shape of the electrodes. Although the detail of these analyses is beyond the scope of t his pap e r , its e ems a p pro p ria t e t 0 i n t rod u c e the sub j e c t. Fig.l.5 shows a wire of length (1) moving at a velocity (V) in a direction perpendicular to the flux (B) of a permanent magnet. The voltage generated between the ends of the wire is 1.3

\_.-)

B. 1. V.

Fig.

1.5

Ge nera t ion 0 f em fin moving in a magnetic

a w ire field

If the wire is now removed and a length of non-conducting tube is placed in the magnetic field as shown in Fig.l.6, we have the basic coniponents of an electromagnetic flowmeter and we may imagine filaments of liquid spanning the tube and each generating a voltage b~tween their ends as they pass through the magnetic field.

11-9

b • ---+-

a • --

---+-

Electrodes

FlOW\;

Fig.

Fig.

1.6 Ex ten s ion 0 f the concept to a flowtube

1.7

Effect of position on induced emf

Referring now to Fig.1.7, a transverse filrnnent (a ) at the centre will generate a voltage between its ends of B.I.V, whereas a filament (b) located nearer to the side of the tube is shorter in length and will probably move at a lower velocity so that the generated voltage is, say, B.I.V/2 whilst a filament (c) nearer to the edge of the magnetic field will probably move at a velocity (V) but be in a magnetic field .strength B/3 so that the voltage generated between its ends is B/3.

1. V.

Thus, the potential across each filament will be different, so that if the ends of all the filaments are connected together, currents will flow in various directions and the signal developed across the filament (a) will be reduced. In spite of the complexity of these Circulating currents, the actual signal (U) developed by the flowmeter for a range of ideal conditions, including a uniform magnetic field and axisymmetric flow, is

where

U

B.D. Vm

B

the flux density the diameter of the tube the mean velocity

o and Shercliff for predicting

Vm

suggested the weight function (W) as a means the effect of distorted flow profiles such that

11-10

1/y_ Y:l. dr

'U

where

the velocity the weight function the radius

V W

and

r

Fig.I.8 shows this weight function for a uniform magnetic Bevir has shown theoretically that W

wheje

:::

B x

field.

I

B is the magnet i c flux dens i t y and I the curren

t

w"'"

c Fig.

1.8

Weight

function

for uniform magnetic

field

density that would be set up in the liquid if unit current was passed from one electrode to the other through the liquid. The requirement for the actual signal (U) developed in the flowtube to be independent of the velocity profile and only dependent on the total or mean flow rate is that ~ W o. Flowtubes have been designed with weight functions much more uniform than those depicted by Shercliff for a uniform I 1-11

magnetic

field.

straight

upstream

conditioners, turbines, 1.4

Consequently

as

lengths

of pipe

is the case

and other

Signal

there

types

is no need

or the

for such

inclusion

for orifice

plate

long

of flow

systems,

of flowmeters.

Processing From

a signal

processing

viewpoint,

the

flowtube

can

it were possible to provide an alternating magnetic flux of stable amplitude, then measurement of the signal at the electrodes would be sufficient to provide the indication of the mean flow velocity. In practice, this is not possible; therefore the actual values of the flux and flow signals must be measured simultaneouly and the flow velocity determined by dividing the flow signal by the flux signal. be represented

as shown

r·----------, I . I I I

in Fig.l.ga.

If

r I I

I

I

I

Gain

I

Ratio

CXltput

I

I I

I

I

I

I I I ,

I

~ L. _.

o flow

alance~------

I

J Flowtube

~

~

Fig.

~=~~:r

+--Mains Supply

1.9a

-

\.AA.A..)

Fig.

1.9b Voltage

loge

Current Reference

Reference

Fig. 1.9

Fig.

Basic components of Signal processor for ac excitation

The two principal methods of deriving proportional to the flux involve measuring

11-12

a signal that is either the current

o \

that flow s.th r0 ugh the co i 1 s 0 r the vol tag e t hat i sap p lie d across them (as shown in Figs.l.9b and 1.9c respectively). Both methods represent a compromise, because in neit er case is the reference signal strictly proportional to the flux within the tube. The eddy currents in the metal tube as well as variations in temperature and supply frequency introduce their individual errors and it is a matter of opinion whic provides a better reference. Suffice it to say that over the past decade the current referenc.e system has become more widely used. Other methods that have been used include the provision of an add i t ion a I "s ear ch reo iIi nth e rna gnet icc i rcui tan d the use of a Hall effect probe to measure the magnetic field. However both suffer from the limitation that they do not measure the field within the tube and in other respects do not show advantages which would justify the additional cost and complication. Systems with sinusoidal excitation of the electromagnet The functional diagram of a transmitter involving this mode of operation is shown in Fig.I.IO. The flowtube electrodes are connected via a special double screened cable, shown in Fig.l.ll to the balanced inputs of the high impedance input amplifier. To minimise the loading effect of the cables, the screen associated with each input signal is driven by the (1)

HIGH IMPEOANCE INPut AMPLIFllRS'

VOLTA E OUTPUT· [E96R ONL YI-

CALIBRATION

OUTPUT CURR ENT

ZeRO ADJUSTMENT

ZEROADJUST·

'-lENT .__---~

"QVTPUTISSELECTEIl BV LINK ARRANGEMENT

Fig.

1.10

Functional

diagram I 1-13

of

transmitter

MINIMUM SIGNAL LOCK

OUTER SCREEN__ ---<>TRANSMITTEA POWER EARTH

DRIVEN SCREEN

DCHROME VINVL. JACKET Fig. 1.11

~ ~

ALUMINUM MYLAR SCREEN

Screened cable used for the electrode connections

output from the first stage. Even so this loading does have an effect on the overall performance of the system, an effect which is determined mainly by the length of the screened cable and the conductivity of the measured fluid. The output signals from the first stage are also applied to a differential amplifier, which provides an overall gain of about 10 but has a very high common mode rejection. The reference signal which provides the measure of the magnetic flux in the flowtube is derived from a voltage transformer connected across t he sup ply _tot he flow tub e • The signal is first shifted in phase by 900 and then applied to the zero crossing detector to generate the synchronising signal for the two synchronous rectifiers, one of which operates on the flow Signal and the other on the reference signal to generate a dc signal proportional to the magnetic flux. The same phase shifted signal is applied to an inverting amplifier with a potentiometer connected between the input and output to provide an adjustable voltage which can be combined with the output from the differential amplifier to balance out the residual no-flow signal in the system. After synchronous rectification and buffering, the two signals are applied to a circuit that produces a square wave having a duty cycle linearly proportional to the flow signal. This comprises an integrator, a comparator and a reference signal amplifier whose gain is switched between +1 and -1 as shown in Fig.l.12. In operation, when the flow signal is zero,

11-14

{'--

COMPARATOR

FINE SPAN

ADJUSTMENT

REFERENCE SIGNAL

Fig.

1.12

Signal

dividing

stage

in the transmitter

the reference voltage alone drives the integrator until its output reaches the trigger level of the comparator, whereupon the polarity of the output from the reference amplifier is reversed; as a result the integrator output is driven in the opposite direction until the comparator resets. Under these conditions the comparator output is a square wave having equal mark/space ratio (or unity duty cycle) as shown in Fig.I.13. ~en a flow signal is applied, the integrator ramps more quickly in one direction and more slowly in the other caUSing the mark/ space ratio of the comparator to vary in proportion as shown in Fig.I.14.

,vtvA A 'lJiltjl

INTEGRATOR

INTEGRATOR

-v

~

V

L

COMPARATOR (TRIGGER)

Fig.

1.13

COMPARATOR (TRIGGER)

.v~ ~

N

Fig.

Waveforms wi th no f low

L 14

~

L

Waveforms wi th f low

This pulse drives a photo-coupler to provide the necessary galvanic isolation between the input and output circuits. Thereafter the signal is shaped and applied to a 'mark/space' I I -15

ratio-to-voltage in the variety same moving

range

converter

is also

coil

generates

0 to 10 V dc, which

of controllers,

signal

which

meter

alarms

used

may and

within

if this

be used signal

the

feature

a proportional .as input

signal to a

conditioners.

transmitter

is specified

The

to operate and

to drive

a a

vol tag e - t 0 - cur ren teo nv e rte r wh ich ge nera t est he s tan dar d 4 to

20 rnA dc (0 rIO

to 50 rnA dc ) s Ign a I for

t

ran sm iss Ion p u.r po se s .

Systems with unidirectional excitation of electromagnet Systems of the genera] type described in the previous section have been in service for more than two decades during wh ich nume r0 us ref i n ernen ts have be·en i n trod ucedin bo t h the me chan ical con s t ruc t.i on and the .meas u rernen t c ircui t s . Bu t the need to improve the zero stability and to reduce the power consumption led to the introduction of alternative modes of operation. An improvement in both respects was effected by replacing the sinusoJdal excitation of the magnetic field at mains frequency with a system shown in Fig.l.15. (2)

~Q_{Sample Hold _.

I

I

I

l-- ,...-.....,I'~-' I

,1_.1

I -- .,..-......

I_L_

pmcted I.------. l1easurement

Signal

l

~

Flow

Signal

F'Ig , 1.15

:><:_ 7 Zero Signal

Waveform for electromagnetic flowmeter with unidirectional excitation

In this system, the electromagnet is energised by applying the rec t i fie d rnains and the n, a ft era few cyc 1 e s duri n g w hie h the current stabilises at a value determined by both the

1I-16

impedance

of the electromagnet

voltage, The

the

signal

excitation

sampled

has

again.

switched

fallen

Subtracting

the electromagnet

of the

flow

rate.

The virtually

the

However, flux

adjustment

since

is steady

frequency,

is not as those

the

signal that

in the is

obtained

and

a measure

to the variable are

greatly

reduced

required. this mode

used

for

effect

of operaion

the ac excited

signals

for the samll

transformer

due

supply

stored.

provides

interface

the measurement except

the

the current

from

errors

required·for

same

and when

is energised

In this way,

flowtubes

and

signal

of the electrode/liquid

a zero

is sampled

the electrode

this

when

and

of

off

to zero

stored kinetics

the magnitude

at the electrode

is then

electromagnet

and

are

ripple signal

are systems.

sampled

when

at twice

the

mains

is virtually

eliminated

sely rei ate d to. the co iI current because the eddy currents which are induced by the alternating magnetiC field have fal len to a relatively small value by the time the flow signal is sampled and the magnetic field which they create has a negligible effect on the main magnetic field. Fig.l.16 shows the functional diagram of the transmitter. and

the rnag net ic flu xis

rnareel

0

Flowtube

r __ -_ - -- -- _--, !

I I

•

1-----

.....

f out o to 10 KHz f out Engineering

Units 4 to 20 rnA de

Mains Supply

Fig.

1. 16

Fun c t ion a I d i agram '11-17

0f

tran sm itt e r

A signal provides

from

the mains

two output

trigger

signals,

generator

and

signal

to the trigger

cycles

of the mains

for the next repeated. mains

supply

ripple

one

generator

cycles

a result, causing

after

the

transformer

The magnetic

field

proportional

to the

flow

be developed

across

the electrodes.

signal

is applied Referring

generated,

as one

again

starting

of

of th~

cycle.

is in effect

during

the period

and

when

value

coils.

causes

a small

voltage,

through

the flowtube

amplification,

its second the

twelfth

so that flux

butwith

to

the

junction.

output

fourth

to synchronize

the magnetic

at the high

flowtube

of the

an integrator)

the

frequency

to a summing

again 'from

It is used

from

a mains

After

inputs

is then

in the

liquid

at the beginning

(which

stabilised

rate

to the counter,

to the end of the eight the sixteenth

creates

the sequence

with

up

this

inoperative

is energized

current

on it to build which

and

The

for eight

it is held

of the mains

the

circuit.

it operative

which

which

synchronizes

the detector makes

a direct

superimposed

to a counter

of which

the other,

supply,

eight

As

is applied

is

mains

cycle

through

to

the detector,

it is only

is either

the small

operative

zero

or has

superimposed

ripple. The

detector

which

generates

rate

proportional

second

output

resistor,

voltage

resultant detector

integrates magnetic

and

regardless

signal

developed

the coils,

is proportional

with

reference

ensures

proportional of variations

the dc-to-frequency

circuit 11-18

to generate flux.

during

the periods

to the is also

from

it only

constant frequency

liquid

in mains

stage.

to the detector.' so that

the

is

signal

signal

that

a

voltage

the amplified

or at its essentially

system

is used

is applied

appear

across

the dc-to-frequency

by the sync which

of the

to the magnetic

this

generated'by

the difference

is zero

feedback

with

is combined

the signals

is accurately

flowtube, from

signal

the period

the

stage

and at a repetition

During

circuit,

is 'gated'

flux

This signal

in series that

duration

input.

the counter,

by the pulses

the electrodes The

to the dc

from

to a dc-to-frequency

of constant

frequency/reference

modulated The

is applied

a pulse

connected

a reference In the

output

when high

value.

output

flow

voltage.

used

the

to drive

rate

in the

The

signal

a scaling

counter units

so that such

as pulses

frequency-to-dc to 20 rnA dc

\

_)

the output per

stage into

which

it generates

litre.

which

In addition

generates

a resistive

is in engineering

load

up

there

a current to about

is a

in t e range 1500

0

4

ms.

(3) -Systems with bi-polar excitation of the electromagnet A further refinement of the concept involves energisation of the magnetic circuit first with one polarity for a fixed period, then removing the excitation for a similar period ~efore energising it in the reverse direction, and so on. The advantage claimed for this system is that it further reduces the errors due to polarisation at the electrode fluid interface. Also, the coil drive circuits are arranged to optimise the speed at which the current reaches a stable value at which it is held during the signal sampling process. Thus, the speed of response is enhanced and the effect of eddy currents is eliminated because these only have an effect whilst the current is changing and the measurement signal is taken after they have died away_ AI~o the transformer Signal is virtually eliminated. PULSERATE .' I'I!AINSFRE()U~NC'l'

CLOCK (LOGIC CIRCUITI

POSITIVE

CUARENTON I CURAENT, ON PULSES fROM LOGIC

crncorr

!

~ __~

• OVE!,O,RIVE

r

~rJ J

I

1

1

I

:STABLf!

I

NEGATtVECURRENTON

I......_

_

I

I I I

COil CURRENT FROMCOil DRIVER

REFERENCE

VOlTAG~ FROM COIL DRIVER TIMING PULSES FOR !.lEAS,ANO REF_: LAGAND ~OLD TIMING PULSES

:

;'~=;~~~~~TTIC

I ;-.------'

TIMINGPtJlSES

I

;.-1

FOR SYNCHRONOUS RECTIFIER

Fig.

C ACUITS: ACTIVATED

1.17

CIRCUIT I ACTIVATED

--;

'------

-

---'1

Waveforms for an electromagnetic with bipolar ex c i t a tf on 11-19

flowmeter

shows

Fig.!.17 is synchronised switched

how

with

the mains

on for a period

it is switched the coil

off

current

the excitation

for

supply.

of four four

is switched

The

cycles

cycles.

of the magnetic current

of the mains

After

on again

coil

for

this

circuit

after

quiescent

four eycles

c u rre n t now flows

but

is which period the

in tbe reverse direction. At the end of this period it is switched off fo~ four cycles and then the entJre sequence is repeated. During each period in wh ich current is app li ed to the coi I t .t he lo-gic circuits synchronise the sampling and holding for botb the flow signal and the coil curren-t, as well as the ope rat ion oft he vol tag era t i 0 to .d u t Y ·cY c I e 'c0 nve rs ion • Th i s latter circuit operates at a nominal kHz with the d ut y cycle arranged to be 15% for the lower range value and 85% for the upper range value. Fig.l.18 shows how other optional feat~res are provided. These include an integral moving coiL meter to monitor the output signal, a digital flow rate meter and pulse output for dr Jv i ng an electromechanical .coun t e r . This circuit is adjustable be tween O. 1 and .1 0 Hz (-corres pond i ng to the upper r.an ge va 1ue) and pro v ide s a 24 V s ign a 1 5 0 ms d u rat i.o.n a to. 2 5 A. I not her respects, the instrument has evolved from previous designs.

~~~~T~:~I«J

OU'PuT

ro"'TROI.CO~TlON"'ll

--
E.. PTY TOSE

---0

"'LAlit.! CONTACTS

i

L..-

?:;~~~~~ RA ~

.NChCATO" r4 r01O""AIIllPUTI

--'-

1 NIGH

'5OLUTIO~ EAAT~ ~~

"

WF

IMP(D"'NCE I~PUT eUFfER

1 I

GAI~ ..lND

_j(>. __ RANGE ~>'AD.."\)5rMl"" STAGl.5

_jf

-·1'"

.~

~

ELECTROO:>ES

~

FLOWTUBE

:~~~II.I'''C( STAG~

':-

COlI. OAIVER

r

4U10 ..ATIC lEAD '''TEGRATO~

1

~:';;';'::"__'!-----I

OI(jIT.AL RAl[

4--_·

REf(.(NCf.

",rnA

1----1

I--<>

L----I-----tShECTEC'

jl

r-- ~~; I------t-------____;;-..... ~OlO

PULSE OUTPUT . 0'110"

1----------1

___________ -----r-..1....-

Il"TlO"".

",-"S[ ~T

ClOC,.. 11ttJ\H ., ,,-,,-,.. S HUlIuLN(.'t

I-,..--_j1

I

I'OWE.A: UAtNS 150CA.eo WI'

Fig.

1.18

Fun c t ional diagram 11-20

of the transmi tter

1.5

Installation

Requirements

lowtubes themsel yes may be mounted ln any pas it ion provided that the associated pipework and plant are arranged so that the flowtube is always full. The preferred arrangement is for the axis of the flowtube to be vertical and the flow to be upwards as shown in Fig.l.19. This is particularly so if the process fluid is a slurry. If the flowtube is mounted other than with its axis vertical then it should be orientated so that the axis of the electrodes is horizontal, as shown in Fig.l.20, to minimise the effect of entrained bubbles which not only give rise to volumetric errors but may also interrupt the flow signal to the electrodes. The transmitters are available for integral mounting on the flowtube as shown in Fig. 1.21 or separately on a 50 mm (2 inch) pipe or on a surface. The

f

--J

1 FLOW

AXIS

Fig. 1.20 Orientation of electrodes with flowtube horizontal Fig. 1.19 Preferred installation of flowtube

Fig. 1.21 Intergral mounting of transmitter on flowtube

I 1-21

FLOWTUBE

For

the systems

the mains that

supply,

the mains

transmitter changes shifts

rather

of one

detectors

is taken

than

or other supply

modify in the

the

it is important

supply

in one

turn would

in which

from

to arrange

a separate

and

via

rise

load

cause

and

phase

this

of the phase

so give

so

the

as

could

to the other

the synchronisation

from

the wiring

circuit,

two circuits

respect

transmitter

is excited

to the flowtube

of the

with

flowtube

in

sensitive

to measurement

errors. As mentioned installation

previously,

so that

developed.

This

was

it is desirable

the velocity

profile

particularly

true

to arrange

of flow

an

is well

for earlier

designs

of

for present designs a straight section 5D long immediately upstream of the flowtube provides sufficient conditioning to reduce velocity profile errors to less than 10/0. Electrical continuity between the flowing liquid and the metal body of the flowtube is required to provide the reference potential for the measurement signal. With unlined metal pipes connected to the flowtube, continuity is provided via the flange bolts, but with lined or non-conducting pipes, earthing rings must be fitted at each flowtube flange as shown in Fig. 1. 22. flowtube,

but

EARTH

Fig.

1.22

Installation

of earthing

rings

These rings are circular metal plates each having a tab for the electrical connection and a concentric hole slightly smaller than the bore of the flowtube. In some modern flowtubes, the earthing rings are included in the basic design to minimise II-22

the calibration distortion flowtube

of both due

fabricated

which

would

the magnetic

to the adjacent

from,

or

material,

errors

magnetic

non-magnetic

otherwise

be caused

and electric

flanges

material,

field

and pipework non-magnetic

and non-conducting

by

within

the

being but

conducting

material.

1.6

Factors Influencing Choice of an Electromagnetic Flowmeter As has been mentioned previously, the majority of flow measurements in the process industries are made using a primary device (such as an" orifice plate) to create a head loss and hence a differential pressure that can be measured by one of the many different types of transmitter that are now available. Fig.1.23 shows that, for line sizes greater than about 75 mm, this is the least expensive system and it is supported by a vast amount of practical experience. The measurement or output signal can be a pneumatic pressure, electronic current or frequency, and there are many suppliers of these devices. Consequently choice of an electromagnetic flowmeter system must be jus t ifie d by 0 ne 0 r mo reo f 'the f 0 IIow i ng f eat u res ;

£30JOOO~-------+-------4-------r-------+-------r-------r----~'__

0':.;/

COST Turbine

i

Electromagnetic £l,OOO~------~-------+-----;\Mr--~~~--~~~~-----r------~ " Orifice Plate + dIp cell £300-+------~-------+------_r------_r------,_------_r------T_1 mm

3mm

10 rom

30

mm

100

rom

300

mm

1

LINE SIZE

Fig.

1.23

Costs versus line size for various types of flowmeters 11-23

m

3

m

1.

2. 3.

4. ~. 6. 7.

Low head loss, and hence suitable for measuring the flow of slurries. Insensitive to changes in temperature, pressure, . density and viscosity of the process fluid. sensors and hence suitable for Non-invasive ·applications where strict requirements for hygiene are imposed. Linear relation between flow rate and measurement signal. No moving parts, no hysteresis. Suitable for measuring flow of aggressive fluids. Insensitive to swirl and pulsatile flow.

These features are supplemented by the more general characteristics of wide rangeability, good accuracy and repeatabjlity, and availability in a wide range of sizes. However t her ev a re two distinct limitations, namely: 1. The fluid must be an electrolyte (i.e. conductive) and consequently the system is unsuitable for measuring the flow of gases or liquid hydrocarbons. 2. The systems require relatively high power for their operation and therefore they cannot be intrinsically safe. In spite of this, the unique features of electromagnetic flowmeters are sufficient to sustain their position as a principal alternative to the orifice plate/differential pressure systems in spite of the higher cost. Fig.l.24 and 1.25 provide a comparison with the other methods of measurement.

11-24

LINE

0.3 mm

1.0

3.0 mm

tm1

10

111m

100

111m

300 mnl

ntn

1000 moo

3000 mm

I

I

Orifice Plate"

III 11I1_-"'

IIntegral

SIZE

)0

__

dIp

"

"' __

""I1I1IIU

Ori fice

1111111

11111111

Venturi

III [111_"'

"' __

IIIIIII.)~_._. 1111111 11111111

"

••

Electromagncl.lc "

•

__

.11111111 J 1111111

:~ 1111111

;3q~et

__

"

N~z:z.le

"'1111111

"'

J

Vari~ble Arc!

,111111_-_---

11111111'

11111111:-•

I..

.

r(lS~tlvC DISl'iac:cmcnt "11111111

1111111••

__

Turbine

"'

1111 1I1 __

__

•

.1111111:

Vortel( •

..

__

~1I111111

nr'III_--I---·····11I111I: ut trasonic.

Fig.

1.24

Ava i 1ab nit y 0 f f 1owme t e rs for various line sizes

ACCURACY

0.1"%

0.3%

1.0%

10%

I

Orifice

p~ate

II 11111

+

I

dIp

1111 1111 Integ. r~l Orific€:

11111111 Venturi •

1111111 __

11111 11 111 1111

/ No?zlc

til

11I1I11I_"'_~_.1I1l1

T .. rgct

JlIIIIII

11111111

EIeccrcmagne

11111111.

""

t Lc

__

."

11111 Variable Area

11111111

1IIIIi_,,

Posi__ t ivc Displacement ~

1lI11111.

111.---.---_.

I 1l111!

1(1I1l1111

Tu rb ino

1111 I

1111 111 __

•

Vortex

11(1111 ,,11111111

11111111

Ultrasonic •

IIJJ 1(11111111

I Fig.

1.25

General off

accuracies

Iowme t e r s

11-25

of various

types

1.7

Industrial There

are so many

flowmeters control

Applications

involving

loop

illustrate

that

applications

only

to cite

be a difficult An example in a coordinated paper

stock flow

of several

shows

its associated

more

than

characteristics

to overcome

what

of

otherwise

would

problem.

electromagnetic for a paper

the

and

little

is the blending

how

of softwood,

do

of the unique

flow measurement system

instrument

them would

is used

and additives

Fig.l.26 the

a single

how one or more

.this 'type of flowmeter

of electromagnetic

flowmeters

hardwood

flowmeters

operating

of the various making are

and broke

types

of

machine. arranged

stock

to measure

so that

it can

a

digital blend control and the correct quantities of dye and additives such as clay, alum and size introduced in the required proportions. The paper stock, which typically includes between 3 and 5% by weight of solid material, is a particularly difficult material to meter, and the non-invasive sensors, together with the high accuracy that can be achieved, make the electromagnetic be blended

continuously

under

control

of

DIGITAL BLEND CONTROLLER SOFTWOOD

HARDWOOD

8LEND CHEST

..... -

TO PAPER MACHINE

Fig. 1.26

Use of electromagnetic flowmeters for paper stock blending II -26

flowmeter The meter

dye, but

the only alum, can

instrument

clay

and

be handled

size

suitable are also

for this difficult

by electromagnetic

application. materials

flowmeters.

to In

an the

actual application, the transmitters would be provided with pulse output circuits so that a digital blending controller operating in conjunction with a level controller maintains the correct level in the blend chest for supplying to the paper making machine. Another example of the use of several electromagnetic flowmeters in a process is the 802 scrubber ·s h own i n Fig. 1•27 •

STACK GASES

TO REGENERATION r--CONTROL

I

.

"'--""I-~_.L_Q YALKAllNE

REAGENT FLUE GAS

l PHT

SCRUBBER RECYCLE TANK

Fig.

1.27

Use of electromagnetic an S02 scrubber

flowmeters

in

The scrubbing action is effected by spraying a lime based slurry into the flue gases as they rise up the scrubber tower. The liquid that collects in the bottom of the tower is transferred to the recycle tank where the pH is measured and any deviation from the desired value is transmitted as the setpoint to the flow controller, whose measurement signal is 11-27

derived

from

reagent

line.

prevent

underabsorption

leads

the electromagnetic In this way,

to scaling

as unnecessary control with which

loop

another

reliable

of S02 of the

includes

fluid

The

fluids

is controlled

of the scrubber lime

slurry

flowmeter

is withdrawn in this

for measuring

11-28

which

in conjunction the rate

all have provides

rates.

as well

A further

for separation

flow

to

also

nozzles

controls

flowmeter

slurry

accurately

which

process

their

lime

reagent.

transmitter

so that the electromagnetic method

in the

at low pH values

a density

electromagnetic

the process

solids

the pH

and plugging usage

regeneration.

flowmeter

at

or entrained the only

Chapter

2

ORIFICE PLATE FLOW MEASUREMENT

2.1 .At A2 C D d

m

r

s y E

p U

v

Notation Area of upstream pipe Area of throat or orifice Discharge coefficient of flowmeter Upstream diameter of flowmeter or inlet pipe Throat or orifice diameter Ar ear a t i 0, {= (d10) 2} Absolute pressure upstream of flowmeter Absolute pressure at throat or downstream tapping Pressure difference (= PI - P2) Flowrate Pressure

ratio,

ie [ 1 -

p 1 - P2 \

PI

J

Mean

velocity

at upstream

section

Mean

velocity

at throat or downstream

section

Flow coefficient Flowmeter diameter ratio, (= diD) Ratio of specific heat, (Cp/Cv) .Expansibility factor Density of flowing fluid at upstream section Dynamic viscosity of the fluid Kinematic viscosity of the fluid (= u/p)

2.2

Introduction The orifice plate flowmeter is one of a group'of flowmeters which operate by creating a difference in static pressure between the upstream and downstream side of the de vic e • It rnay be ins tal 1 ed e i the r 'i n - 1 i ne " ie wit h pipework both upstream and downstream of it, or at the inlet to or outlet from a length of pipe. Other types of 11-29

differential

pressure

meters

are:

low-loss

nozzles venturi

tubes

inlet

venturi

nozzles

variable

together

differential the most favour

in use

pressure

popular especially

venturi

tubes

large water

plate

devices,

were

mains

used

with

over

the orifice The

nozzle

inclusively

the world

meter).

60 per cent

at the present

flow measurement

almost

around

(Target

that well

country.

for steam

electromagnetic

flowmeters

in industry

in this

tube)

area meters

it is estimated

of the flowmeters

(eg Dall

flowmeters

drag All

devices

until

time

are

plate

being

has been

in

in Germany

while

for measurements the advent

in

of the

flowmeter.

The main

advantages

of pressure

a

they

are

to make,

b

their

c

they

difference

flowmeters

are: simple

performance are cheap

compared

with

containing

is well

in larger

they

can be used

in any orientation,

e

they

can be used

for most

main

disadvantages

their

rangeability

other

types

pipes

when

meters,

d Their

parts,

understood,

- especially other

no moving

gases

and

and liquids.

are: (turndown)

is less

than

for most

of flowmeter,

ii

significant

iii

output signal is non-linear with flow, the discharge coefficient and the accuracy may be affected by the pipe layout and/or the nature of flow, and they may suffer from ageing effects, ie the build-up of deposits or erosion of sharp edges.

iv

v

pressure

loss may

occur,

The fundamental Bernoulli equation which deals with the relationship of the static and kinetic energy along streamlines in a fluid stream can be used. Simplified, this 11-30

L Fig. 2.1 shows that in a converging between two planes is:

Converging

flow

pipe, Fig.2.1,

the energy

equation

(2• 1 )

\'.._,)

The equation section this can

other equation which can be used is the continuity which states that the mass flowing past any crossin a pipe remains constant. For incompressible flow be written as: (2•2)

wnere

= m

By substituting

(area ratio).

(2 .3 )

for vI and v2 it can be seen that (2•4 )

Q

This equation is valid only if no losses occur and if the moving fluid completely fills the areas Al and A2" In reality neither of these assumptions is valid and the discharge coefficient, C, has to be introduced to compensate. The discharge coefficient can therefore be defined by,

(2•5 )

c

II-31

The

term

1(1

- m2)

is known

as the velocity

vI

of approach

v2'

» A2 and therefore « 1(1 - m2) Instead of the area ratio the preferred term tends to unity. use din t ern a tion a I1Y i s the d iarnet err a t i 0, 13, w her e : factor.

Where

Al

d D

and

the diameter d being the bore diameter and D being the upstream pipe diameter. Another form of coefficient, the 'Flow Coefficient' has been commonly used in Europe and this is given by

a,

(2 •6 )

In nozzles and venturi tubes the flow follows the b au ndar y 0 f the wa lIs c lo sely and the val u e S 0 f Car e u sua 11 y c lose to un i tY • Howe ve r, inth e cas e 0 f the 0 r i f ice p la te the flow continues to converge downstream of the plate forming a 'vena contracta'. The area of this cannot practically be measured and is thus not known accur~tely. In calculating the discharge coefficient therefore, the area at the orifice bore is used which leads to a value of C of approximately 0.6. Th is, i n e ffee t, inc Iude sac 0 e f f ic i en t 0 f con t ract ion. If the fluid being metered is compreSSible, there will be a change in density when the pressure of the fluid falls from PI to P2 on passing through the device. As the pressure chan ge s qui ck 1y, i tis ass ume d that n 0 he a t t ran sfer 0 ccur s and because no work is done by or on the fluid, the expansion is isentropic. In nozzles and venturi tubes the expansion is almost entirely longitudinal and an expansibility factor, E, can be calculated ass~ming one-dimensional flow of an ideal gas. For orifice plates the exp an s i bI 1ity correction factor has to be determined experimentally both because the contraction is not known exactly and changes occur in the jet. The expansibility factor is thus a function of the diameter ratio, the specific heats and the pressure ratios (P2/Pl). The full equation for.the orifice plate flowmeter in compressible flow is therefore U -32

r'

Q

2.3

Orifice

Plates

=

(2• 7)

and Pressure

Tappings

(1)

Forms of orifice plates Many different geometrical profil~s have been tried in order to obtain constant discharge coefficients over as wide a range of flowrates as possible. Examples of these can be found in the literature but the distinctive features of these devices are that there is, a flat front and back face and the variations are in the profile of the bore and to the immediately adjacent areas of the face on either side. 0:0.10

t--

0.5D ~O.02D for Il ..0.6 0.5D :t O.O!D for f3 :> 0.6 ond 012 Pressure 'toppinqs

o

Flonq. toppings

a Thickne$S'E of the plate

II

b Fig. 2.2

From

(a) Location of ISO 5167 pressure tappings upstream and downstream of orifice p]ate (b) Details of ISO 5167 orifice plate

the early days of the orifice

II-33

plate

in the 1890s

however bore

the most

diameter

upstream may

face,

be bevelled

plate

exceeds

the plate

widely

is cut out Fig.2.2.

used

plate

to give At

is limited

a square

the downstream

if for strength O.O·2D but

has been

reasons

one

edge

with

end,

the outlet

the

thickness

in all cases

the maximum

This

is because

to 0.050.

in which

the

the of the

thickness

of

the

streamlines of the emerging jet will be influenced and hence the contraction coefficient and the discharge coefficient will be affected if these limits are exceeded. At the other extreme a minimum of 0.0050 has been adopted for the overall thickness of the plate. This form of orifice plate, commonly known as a 'sharp-edge' orifice plate, was standardised in the USA in the 1920s, followed shortly afterwards by standardisation by DIN in Germany and then adopted in the late 1930s by the ISA subsequently became Internationa\ Standards Association. the International Organisation for Standardization, ISO, under whose aegis the world's flow measurement standards have subsequently been published. The present version of the interna·tional standard on orifice plates is ISO 5167. The present author has described how this standard has emerged from the earlier work and the dom ina n t feat u res wh ich are a t pre sen t the sub jec t 0 f some controversy and the objective of major experimental programmes in this and other countries in Western Europe and in the USA and Japan. ~ile the normal profile used in orifice plates is thus square or sharp edged, conical-entrance and quarter-circle plates are also used, especially for viscous flow. The downstream edge of a square-edged plate can be bevelled, unless the plate is thin, whereas the downstream edges of conicalentrance and quarter-circle plates are square. On the other hand the upstream edge is a cone or circle and these shapes show a near-constant coefficient down to quite small Reynolds numbers. For special purposes, eccentric or even non-circular orifice plates are used; for example, in metering suspended solids a chord-type orifice plate can be used, Fig.2.3.

11-34

CHORD

Fig. 2.3

Chord-type

ORIFICE

PLATE

orifice

plate

Having established the general concept of a constant discharge coefficient it will seem strange to refer to limits on the flow range for which orifice plates can be used. In practice, however, fluids are not ideal and frictionless and the velocity distribution in a pipeline as well as the turbulence pattern, even if the pipeline is very long and uniformly straight, will change with the characteristics of the fluid and its flowrate through the pipe. A parameter which has been found to give a generalised picture of the flow pattern inside such a pipeline is called the Reynold~ number. It is defined by: Re

('2.8) II

\)

The mean velocity in the pipeline, v, is clearly a simplified idea of what is really happening, just as the fluid density has to be an average value, but in the case of a gas may well vary across the cross-section. To a first approximation, however, the discharge co~fficient of an orifice plate will bear a direct relationship to the upstream Reynolds number which is for any specific flowing fluid directly related to the flowrate so that: C = f (Re ) = f (Q) •

11-35

(2.9)

It will discharge

be appreciated

coefficient

value

that

this means

will

be obtained

that with

the same different

ions 0 f flu id. and f 1owr ate. T akin g wa te r ,w it h a kin erna tic vis cos ity 0 f 1 cSt as a base, a Reynolds numbef ~f 100 000 would be obtained in a 100 mn pipeline for a mean fluid velocity of 1 mIse It is predicted that the discharge coefficient for an orifice plate of 0.5 diameter ratio with corner tappings (to be described later) will then, according to ISO 5167, be: comb ina

t

C

=

0.6053.

The same coefficient will be predicted, however, if a gas with a kinematic viscosity of 0.015 cSt is floWing through this orifice meter-run and pipeline at a mean velocity of near 1y 15m /s • Th e rna ss flow rat e wi I I the n bel / 1 DOt hat 0 f the flowrate of the water in the example above. To obtain the same Reynolds number and hence the same coefficient with a thick oil flowing through the pipeline and flowmeter the mass flowrate will have to be increased to get a higher m~an velocity. For a kinematic viscosity of 200 cSt, the mean velocity would need to be an impossible 200 mls and the mass flowrate would be around 150 times that of the wa ter. This flow measuring device is not suitable for Reynolds numbers approaching the transition and laminar flow zones because the discharge coefficient rises and then falls rapidly in a way which is difficult to predict with any accur acy • It cornesin to its own wit h inc rea sin g Re y no Ids numbers in the turbulent region. Indeed tests up to about 40 million suggest that the changes to the discharge coefficients for all Reynolds numbers above 1 million do not exceed about 0.25 per cent. This is applicable to long straight pipes and what are termed fully-developed flow conditions. (2)

Pressure tappings The previous section has dealt with variations in the geometrical profile of the orifice plate and emphasised that 11-36

the most 'sharp

common

edged' In·the

form

is that

orifice early

days

the pressure

plate

drilled

in the pipe

upstream

plate.

In the early

1900s

these.

was measured

locations

In the USA

in ISO 5167

as the

plate.

orifice

own preferred

standardised

the

from

any

difference pair

of tapping

and downstream different

and claimed flange

various

the holes

of the orifice

companies

taps won

across

adopted

advantages

their for

the day and became

ASME Fluid Meters. These are drilled through the flanges perpendicular to the pipe at distances of 1 inch upstream and 1 inch downstream from the faces of the flanges. In Germany corner tappings were preferred and standardised by the VOl and DIN, the equivalents to the Institution of Mechanical Engineers and the British Standards Institution in the United Kingdom. These tappings are drilled so that they are at a slight angle so that they come out with one edge of the tapping hole just touching the face on either side of the plate. These tappings were also generally adopted by other European countries. In the USA vena contracta taps were accepted as an alternative for many years but are inconvenient if the orifice plate bore has to be changed to adapt the pressure difference obtained with changing flowrates. The firm of George Kent's in the UK and others had found 0 and D/2 tappings just as good as vena contracta taps and since they have the advantages of being fixed and non-dimensional they have been accepted in ISO 5167. Thus there are three standard locations for the differential pressure tappings to be placed inthe pipe, see Fig.2.4. standardised

in.

a b c

corner tappings, flange tappings, and 0 and 0/2 tappings.

Discharge Coefficients of Orifice Plates J Stolz, Chairman of the ISO Technical Sub-committee responsible for drafting ISO 5167, led the way to a new understanding of the coefficient relationship with its many 2.4

11-37

controlling

parameters.

attempts

to co-ordinate

preceding

decades

appreciated because acceptable available to be

that

many

been

early based

data

bases

then

on non-standard

D "NO

the

up over

the

It will

be

but

there

still

internationally

Often _.:theraw data

were

not

fitted

data

had

a suitable

to smoothed

data

CORNER

D/2

1970s

to be discarded

to develop

arbitrarily

to provide

built

devices

predictions.

curves

and early

mathematical.

had

in trying

coefficient

interpreted

19605

pricipally

experiments

problems

so that

late

the various

had

they were

remained

In the

base.

TAPPINGS

-_ --_

..Ir •

o

0

-----

t

I

..J..

PeA"' OF ""' 'O""Am

----_

i

PRESSURE ON PIPE WALl.

Fig. 2.4

Alternative

pressure

tappings

Equations using power series were tried and while they may have been excellent fits with the data used to obtain them they were inconsistent with each other, often difficult to use, and dangerously wrong if extrapolated. For exrunple one such equation had terms in powers of the diameter ratio going up to (3.2'+ •

Stolz realized that improvement could only come by recognising that the discharge coefficients derived from different sets of pressure tappings must nevertheless be related to each other by physical laws. Thus the results flange tappings and corner tappings must become identical 11-38

for for

large

pipe

sizes

since

the allowable

physical

locations

then

tappings

must

the same

all

give

coefficients

approach

each

equation

was

the pressure orifice

plate

overlap.

for all other

then

Similarly

results

tappings

on

ratio

small

just upstream independent

bounda r y cond itions to represen

and D and D/2 sizes.

diameters decreases.

to the non-dimensional

distribution based

pipe

on their

flange

at very and

as the diameter fitted

tolerances

must An

measurements

and downstream

tests.

Again

Combining

of

of the

these

log i ca I1Y these 1aws w i th. the tWo sets of data which were the best authenticated (Beitler's in USA and Witte's in Germany), he evolved an equation for calculating the discharge coefficient which was relatively straightforward. The Stolz equation (Tables 2.1 and 2.2) is not necessarily valid for all time but can, with great confidence, be regarded as a satisfactory foundation for accommodating new data merely. by altering the constants. In the author's opinion any updated correlations of data should be based on its principles. Table

2.1

t

The Stolz equation*

C=0.5959+0.0312{32·'-O.184j38

+ O.0029/12.S[ 106]0.75 ReD

+ O.0900L1{34(1

- /14)-1 - 0.0337 L~{33

0.0390 . If L, ~ 0.0900 (= 0.4333) use 0.0390 for the coefficient of {34(1 - {34)-1

* As

given in ISO 5167 (clause 7.3.2.1)

Table

2.2

Values

of Ll and L2' L,=L2=0

Corner tappings D and DI2 tappings

L, = 12; L~ = 0.47t L, = L2 = 2S.4ID:I:

Flange tappings

t Hence coefficient of {34(1 - (84)-1 is 0.0390 :!: Where D is expressed in mm

The .c oe f f Lc Ien t s given by the Stolz equation are only applicable to the type of orifice plates specified in ISO 1I-39

5167 (Fig.2.1) and can only be applied when the conditions use given in Table 2.3 are met (ISO 5167, clause 7.3.1). Another with

condition

an upper

is that

limit

the upstream

of relative

pipeline

roughness

shall

generally

of

be smooth

less

than

k = O.OOlD

(this is approximately equivalent to the surface obtained in a 50 rnm (2 in) diameter new seamless cold drawn steel pipe). The limiting value of k is however dependent on the diameter ratio of the plate being used. Table 2.3

Conditions

Corner taps

d(mm) D(mm}

f3 Reo

~12.5 50~ 0 ~ 1000 0.23 ~ {3 ~ 0.80

of validity

Flange taps

;>-12.5 50~D~760

0.2 ~f3 ~ 0.75

~1260f32Dt

5000~Reo

~ 1OBfor 0.23

~10B

D and 012 taps ;>-12.5

50~ D~760 0.2 ~

f3 ~

0.75

~1260{32Dt ~108

~IJ ~0.45 10 OOO~ Reo ~108forO.45 < {3 ~O.77 20 OOO~ Reo ~108for 0.77 ~{3 ~O.80 t Where D is expressed in mm

Inevitably there will be uncertainties both in the physical measurements to be entered into the flow equation (equation (2.7)) and those associated with the discharge coefficient equation (Table 1). All these sources of uncertainty must be taken into consideration when assessing the overall accuracy of a measurement and another ISO standard, ISO 5168, provides guidance on how to determine this overall uncertainty. The user must estimate the uncertainties associated with his own measurements, but those associated with the discharge coefficient required when dealing with gases particularly at pressures near to ambient, have to be specified. The uncertainties published in ISO 5167 associated with the Stolz equation are given in Table 2.4. As mentioned earlier, different tapping arrangements evolved by custom in different places standardising on such locations out of the infinite number of possibilities which II-40

Ma ny have bee nth e dis cus s-i0 n san d arguments in favour of these and other a rr an.g eme n t s and the Stolz equation gives, theoretically, the coefficient which might bi expected in any combination. The best trusted presently available data, however, are based on the three tapping arrangements illustrated in Fig.2.1 and referred to in Tables 2.2 - 2.4. co u 1d h ave

bee n c h 0 sen.

Table

2.4

Uncertainty associated Stolz equation*

with

the

When {3, D, ReD and kID are assumed to be known without error, the uncertainty of the value of Cis:

{3 ~ 0.6 0.6~{3 < 0.8 O.6~{3 ~O.75

* ISO

Corner taps

Flange taps

D and DI2

0.6%

0.6%

0.6%

{3%

{3%

taps

f3%

5167 Clause 7.3.3.1

2.5

f""\, /

Installation and Other Effects The international standard ISO 5167 lays down quite stringent conditions for the manufacture, installation and use of orifice pl,ates. If an accuracy of 3 per cent or better is considered important then it is vital to conform to these If 5 per cent is adequate it is still ,specifications. nee e s sa ry t0 c omp Iy wit h mo s t 0 f the re qui rernen t s ,bu t pro v ide d the Reynolds number is sufficient, then a simple coefficient value of 0.61 could be adopted for C in equation (2.7) given ear 1ie r . 1 t has to be rememb ere d t hat the ex pan sib iIi ty correction factor will still need to be applied, however, unless the pressure ratio is above 0.975. If accuracies of 2 per cent and better are sought then one of the main considerations must be to ensure that the flow pattern into the orifice meter run is reasonable. All too often the meter is installed just downstream of a series of bends or 11-41'

r0 I val vel 0 cat ed a .sh 0 rt dis tarrce ups tream. Illustrations of the serious errors which can resu-It from not con form ing tot her equi rernen t.s'0 f the s tan dar d can e as i IY be found. In such instances even site calibrations may not resolve the problem since such conditions can produce fluctuations whi~h make accurate measurement impossible. Many experimental studies have been made to try to deal with the co rre ct i on s required to c a t er for pulsating flows and these are i nd i c.at ed in the e a rLi e r ed.ition of the 'British Standard BS i042. The most recent edition of BS 1042 :1982 is technically equivalent to ISO 5167 and does not include pulsating flows. However further parts of the new BS 1042 are to be published within the next year or so - th~~e will give updated information: 1982 and also deal with the other pressure difference devices referred to earlier. Because of the square law relaion between pressure d iff ere nc e and f Iow rat e , the ran ge ab iii'tY 0 fad I: ffer en t ia I pressure meter is limited normal.ly to 3:1 and to about 5:1 at most. This can only be overcome by converting the meter into one capable of multi-range operaion. For example, .a bank of orifice meters of different diameter ratios can be built in parallel and the flow switched to the one with the right range. Ins orne sit u a t ion s wh ere b r ie fin terr up tion -0 f the f Iow is permissible, a greatly extended flow range can be obtained by use of multiple orifice plates. Pressure loss caused by the presence of the flowmeter can po se pro b Iems and Fig. 2 .5 ill u strat est hat 0 r if,ice p I ate san d nozzles because of their design di~sipate most of the energy which creates the pressure difference. Venturimeters are low-loss devices .. wit hac

0n t

2.6

Conclusion . In c ho o s i ng a flowmeter, there are many factors to consider and among them the question of accuracy is very important. ~ile it is pointless to pay for a higher accuracy than is necessary, a cheap meter that is not accurate may be corne ex pen s i vet 0 0 per ate. S iin i 1a r 1y, un 1e ss a me t e r i s calibrated and installed correctly, it will not achieve its 11-42

potential

accuracy.

Thus

a typical

according

to a recognised

uncertainty ideal well

of say

conditions be

effects lengths.

orifice 1-1.5

plate standard,

per cent

depending

increased

size

If swirling

and

'and manufactured

can be expected at maximum

on its diameter

to more

of pipe

designed

than

2.5-3

inadequate

flow

exists

per

flowrate ratio.

cent

upstream then

to give

and

errors

may

under

This

because

an

eQuId

of

downstream rise

to 10

or 20 per cent or more. By calibrating a differential pressure meter an uncertainty of ±O.5 per cent should be obtainable, but this will depend on the quality of the output signal .

. Q. I

f/) (I)

60

9 ~ 50 ::l

f/) f/) LI.J

g:

40

l;j z 30 I~ 20

10 5-7" TAPER 0.1 .

0.2

0.4

0.3

0.5

0.6

0.7

m

Fig. 2.5

Net pressure loss as a percentage pressure difference

of

It must also be noted that the standards only apply to flowmeters correctly manufactured and installed and in the srune condition as when originally commissioned. As time goes on significant errors can be introduced because of age~ng. Thus

11-43

the sharp become

edge

too rough,

orifice

plate.

orifice

plate

transducer

while

may

conditions frequency of the

shift

flows

plate

be eroded,

up against

can

cause

the pipe of the

difference

therefore

predictable

thus

the cleanliness

and

internal

imperative,

the

and characteristics

used.

precautions

flowmeter

are

plate

can

being

observed

be claimed

flow measuring

however,

to be the most device

the reliable

at present

available. Acknowledgements This National Industry, recently

chapter

is published

Engineering East

by permission

Laboratory,

Kilbride

Department

from which

Laboratory

retired.

It is Crown

can

the face of the

dishing

the pressure

of the orifice

upon

these

can

its calibration.

and materials

all

the most

can build

inspection

depending

With

plate

externally

in the pipe

fluid

orifice

debris

Excessive

Periodic

and

of the orifice

copyright,

January

11-44

1984.

of the Director, of Trade

and

the author

Chapter

3

OTHER FLOW MEASURING DEVICES

Introduction Thi s chap ter dea Is wi th f IOWlTIe ter s no t cover ed un de r the headings of differential pressure devices and electromagnetic flowmeters which have been covered elesewhere. The main emphasis will be on volumetric liquid flow measurement although some reference will be made to gas flow measurement. The literature is replete with novel flowmeters designed to meet specific applications, many of which will never enjoy wide industrial acceptance. One estimate puts the number of c OIIIDe rei all y ava iIab Ie f 1owme te r t y pes a t 100 wit h the numb e r cDnstantly increasing. This chapter CDncentrates on flowmeters which have been used successfully and widely in industry. The flDwmeters to be covered are positive displacement; turbine; transit time, Doppler and correlation ultrasonic techniques; variable area; vortex shedding. Particular emphasis is laid upon the ultrasonic technologies which at the present time represent one of the major growth areas in flow measurement, particularly since they offer the possibility of non-invasive flow measurement with the transducers mounted on the outside .of the pipe. For a wider view of flowmeters available the reader is directed to Dowden, A.S.M.E. and Hayward. Brain provides a survey of mass flow measurement techniques. For a regular update on flowmetering the Fluid Flow Abstracts produced by B.H.R.A. Fluid Engineering provide a useful source of material. 3.1

Positive Displacement Flowmeters These flowmeters measure flow quantity as opposed to flowrate in that they deliver a known volume of fluid a measured number of times within the interval for which the flow is to be measured. The known volume can be produced by several means. 3.2

I 1-45 '

For liquid flow this can be by means of a semi-rotating piston, reciprocating piston, mutating disc, or gearing arrangement and for gas

flow

this

or a rotating

be by means

diaphragm.

In the sIfding Fig.3.1a

can

vane

Some

posititve

the set of vanes

of a liquid

of these

are

displacement

rotate

within

seal, shown

a diaphragm, in Fig.3.l.

flowmeter a casing,

the

shown

in

rotation

the flow of the liquid. The defined volume is the volume enclosed between two such vanes, the vanes being arranged in such a way as to provide sealing with the casing and so limit leakage. The liquid monitored should be clean since dirt or grit within the flow can damage the sealing capabi lity of the vanes. The rotation of the vanes is usually recorded by means of a mechanical counter. of the vane

being

aJ

caused

by

sliding vane meter

c) gear

b) 'ova I-wheel' gear meter

meter

Fig. 3.1

d} wet

Positive

gas

displacement

meter

meters

Positive displacement flowmeters for liquids are used extensively in water metering and in the measurement of 11-46

petroleum of order

products. of ±O.2%

They

are capable

of totalised

of achieving

flow with

flow

accuracies

ranges

from

"\

5 x lO-6m3/s to O.5m3/s at pressures up to l04kPa and temperatures up to 300°C. They are sensibly insensitive to ups t r.e am can d i tion s 0 r tot he pro per tie S 0 f the flu i d be ing metered. For further details of the operation of positive displacement flowmeters, see A.S.M.E., Brain and McDonald, Linford and Walker. 3.3

Turbine Flowmeters The turbine flowmeter which can be used for the measurement of liquid or gas flows uses the speed of rotation of a 'turbine within the flow as a measure of the flowrate. As such, the device produces a frequency output proportional to flowrate. The dyrtamical behaviour of the turbine and the balance between driving and retarding torques is'complex. Models for the behaviour of turbines have been produced by Ruben et al and Thompson and Gr~y among others.

coil bearing spacer

housing straightening vane

Fig. 3.2

Turbine meter (by courtesy Foxboro Company)

of the

A typical liquid flow turbine is shown in blades of the turbine come in several forms with helical, or T-shaped blades and various designs are used including ball and journal bearings.

11-47

Fig.3.2. The straight, of bearing Detection of

the rotational detector. to alter

magnets

speed

Magnetic

is achieved pick-up

by means

involves

a magnetic in the tip of the blade which the

reluctance

of

either

of a proximity using

the blades

path or by the use of induce a voltage in the

pick-up coil (Miller). Turbine flowmeters have a fast response to flow and are capable of providing a rangeability from 10:1 to 20:1 (rangeability is the ratio of the highest to lowest flow measured within a certain error band). Calibration accuracies of ± 0.25% of reading can be achieved_with repeatabilities- of ± 0.1%. Typically turbines range in size from 6 to 600 mm. They can operate at temperatures of up to 260°C and pressures up to 2 x 104kPA• At the low end of the flo~ range the reading is affected by the viscosity of the fluid, the pick-off technique, and bearing wear. Overspeeding of the turbine can also detrimentally affect its performance. In order to achieve the specified accuracy of the flowmeter it is usually necessary to have a specified length of· straight run upstream and downstream of the flowmeter. Typically these are specified as 10 diameters and 5 diameters respectively. For high accuracy applications for use in custody transfer situations it is usual to employ turbine flowmeters with a prover system which provides a regular calibration of the turbines. 3.4

Ultrasonic Flowmeters A wide variety of liquid flowmeters for use in closed condu its have been des i gned emp 1 oy i ng U ,I trason i cs, the rnas t common flowmeters using transit time, Doppler and correlation techniques. Reviews of ultrasonic flowmetering techniques have been provided by McShane, Lynnworth who has provided an extensive review of ultrasonic flow measurement with particular emphasis on the ultrasonic aspects as opposed to the electronic aspects and Sanderson and Hemp who have provided a review of the state-of-the-art in liquid flow measurement using transit time and Doppler techniques. Other applications of ultrasonics to the measurement of liquid flow include the measurement of the bending of the ultrasonic beam caused by the flow of liquid 11-48

(Peterman),

and

f I owme te r .

(J 0 y

the detection

of vortices

in a vortex

shedding

and Co Iton, Co 1 ton ) Wit h in 0 pen chan nelf 1 ow and river flow measurement transit time techniques have been employed (Genthe and Yamamoto, Drenthen et a ll . Ul trasonies are also.widely used as the height of determining element in open channel flow measurement employing flumes or weirs.

(I) Transit

u

time flowmeters These measure the time difference between ultrasonic beams transmitted upstream and downstream in the liquid and as such are designed for use with homogeneous fluids. They have been use d for the me as u rernen t 0 f bot h 1 iqui dsan d gas e s .for wh i c h they are capable of measuring mass flow rate as well as volumetric flow rate. (Moffat anf Fetterhoff, Baker and Thomp son) . If the liquid in Fig.3.3 is moving with velocity v at angle 8 to the ultrasonic

and

/

T12

=

T21

::;

sin

sin

beam then

e

d (c-v cos

e

d (c+v cos 8 )

(3 • 1)

e)

(3 • 2 )

where T12 is the transit time from transducer 1 to .t ransducer 2, T 2 1 is the t ran sit time from tran sduc er 2 tot ran sdu ce r 1 and d is the diameter of the pipe. Now since c2»v2 cos2e, the time difference bT is given 2d·cotS·v

by

(3 .3)

c2

i.e. the time difference

is proportional

to v.

For water flowing in a lOOmm pipe at 1 mls with the two beams transmitted at an angle of 45 to the flow, the transit time is 94.3~s and the difference in the transit times is only 88 ns. Since 8T is also proportional to d such measurements are usually restricted to larger pipe sizes and higher velocities. Measurement in smaller pipe sizes is us ally achieved by transmission of the beam axially along the pipe or 0

11-49

by the use of multiple

reflections

along

the pipe

as shown

in

Fig.3.4.

Fig.

3.3

Transit

time

ultrasonic

flowmeter

flow Transducer

Transducer 2 (a) Axial

Fig. 3.4

2

Transducer

1

Transducer 1 (b) Mult ipl e Reflections

Flowmeter

Transit time techniques in small tube sizes

for measurements

Transit time flowmeters can be used either with wetted sensors in which the transducers are in contact with the flowing liquid or as a clamp-on device in-which the transducers are clamped externally to the pipe. Under such conditions the angle e and the required separation of the transducers are then dependent on refractions at the wedge/wall, wall/liquid, II-50

interfaces.

The

two

types

of sensor

are

shown

in Fig.3,.5.

tunqsten loaded resin

piezo-electric

crystal b)wetted

sensor detail

c) clamp-on sensors

Fig. 3.5

Sensors

for transit

time flowmeters

1)

Measurement techniques The two commonly used measurement techniques for transit time f Iowme t e rs are d irec t tran sit time me as u rernen t s, wh i c h are often referred to as leading edge or pulse techniques, and sing-around techniques. Fig.3.6 shows a leading edge technique in which the two piezo-electric crystals are used both as transmitters and receivers, the role change being affected by the multiplexer. A pulse is applied to one transducer, and the time for its arrival at the other is measured. The'system thus sequentially measures T12 and T21. The def~ning equation for AT shows a dependence on 1/c2 and thus the velocity of sound compensation is essential for accurate measurement. Water 20°C shows a velocity of sound temperature coefficient of + O.2%/oC and thus a wetted sensor device would have a temperature coefficient from this effect of - O.4%/oC. I I-51

at

{3.4}

and

i.e.

(3 . 5 )

thus

it is proportional

Pulse

to v and

Amplifier and level

Mul t iplexer

Generator

de-tector

independent

of c.

Time Measurement

output

proportional to flowrate

.: Fig.

Leading

3.6

edge system

Sing-around techniques provided an output which does not require velocity of sound compensation and they operate as shown in Fig.3.7. The received pulse is used to trigger another pu 1·sea t the t ran sm ittera n d the f reque n c y f' 0 f the res u 1 tin g pulse train is measured. The role of the transducers are reversed and a new frequency fll is measured.

f '

sin6(c

+ V

cose)

d

II-52

(3.6)

f" = sinS(c

- v cosS)

(3 . 7 )

d

and

thus

=

f' - f"

__ --

2·sinS·cose·v d

(3.8)

Multiplexer

........... ---1

Rec etver

u L-oI ...............Multiplexer

Fig. One

is that

receiver ~

Sing-around

of the major

techniques Muston

3.7

will

cause

the problem

phase

comparison

technique

difficulties

any

between

in the

and Hoene can

experienced

obstruction

errors

and Loosemore

which

Transmitter

by

sing-around

transmitter

sing-around

have

described

be eliminated.

fig.3.8

and

frequency. a technique shows

by

the pulse

i

division The

technique.

of the output

first

with

the

voltage

applied

In the absence its previous

through

second.

the

Depending

to the voltage of a received

value.

pulses

of the voltage

is transmitted

compared

The

controlled liquid

pulse

oscillator

the pulses

need

accuracy_

Modifications

to the sing-around

it to work

in a clamp-on

mode

These

modifications

which

arises

overcome

as a consequence

have

of refraction

first

the

is adjusted. only

at

2% of

the required

technique

made

the problem

II-53

that

to achieve been

phase

is maintained

it is claimed

in order

is then

arrives

the voltage

by

oscillator.

and

on which

controlled

In this way

be received

are generated

by Yada

of a varying effects.

to allow et ale angle

e

Multiplexer P2

Multiplexer....__-t

t-------4

2 Pulse

.,__........... Multiplexer

Enable

3ms Clock

Fig. 3.8

Two pulse phase comparison

method

2)

Velocity profile sensitivity A single beam transit time flowmeter estimates the flowrate by measuring the average flow velocity in the direction of the beam ac r0 sst he leng tho f the beam. Co n seq uen t Iv : ifit is placed downstream of a bend or valve then, since the fluid velocity across the beam does not represent the average velocity inth e pip e, the f 1owme te r w iIIre ad in err 0 r . Ch ange sin sensitivity of the flowmeter will occur with fully developed flow in long straight pipes as the flow changes from laminar to turbulent. Estimates can be made of the changes in sensitivity due to these effects as follows:If v is the component of the fluid velocity along the sound path and in the direction of the sound travelling from transducer 2 to transducer 1, as shown in Fig.3.9, then at any distance x the sound is moving towards transducer 2 at a velocity given by c + v(x), since in general v is a function of x. Thus the total transit time T21 is. given by II-54

dx

(9.

T21

=Jo

c

+

v{x)

=

R,

c

where V is the average liquid velocity beam along its length 9. and thus

(3.9)

in the direction

of the

(3.IO)

Transducer 2

Fig. 3.9

Api

Velocity

averaging

This mean velocity measurement is not the same· as flowrate. As a result an error of approximately 30% can occur in moving from the turbulent regime to the laminar regime (Fronek), and a change in sensitivity of approximately 3.5% occurs in smooth pes as the Re y n 0 Ids numb e r is chan g ed from 107 to 104• Th e effect of upstream piping such as valves and bends has been estimated by AI-Khazraji et a1 who indicate that large errors can occur with single beam devices. By using a number of parallel ultrasonic beams and averaging the measured mean velocities associated with each, the effect of upstream fittings can be reduced. In this wayan approximation to the mean velocity over the whole cross section can be obtained. Optimization of the position of the beams and the weighting factors applied to the measured mean velocities gives rise to various schemes, analogous to different methods of numerical integration, to make best use of a limited number of beams (Malone et all. Lynnworth and Peterson and Lynnworth describe

II-55 \,

\.

along beam

an alternative employing entire

a uniform

cross

is also

scheme

to the multi-beam broad

section.

a transit

time

beam

The

method

of ultrasound

small

flowmeter

which

involves

extending

over

diameter

tube

axial

in which

a broad

the

flowmeter beam

is

used. 3}

Accuracy Little

transit

time

of transit

time

flowmeters

independent

calibration

data

ultrasonic

flowmeters.

The

is available typical

for

accuracy

q U 0 ted by

a rnanu fac t U re r for a sin g -a r0 un d sy stem emp loy in g wetted sensors is ± 1% of flow from 1 to 12 mls and ±O.009 mls from 0 to 1 mls in a 75 mm pipe. In larger pipes from 100 to 600 mm the quoted accuracy of ± 1% of flow extends over a wider range from 0.3 to 12 mls with an accuracy of ± 0.00455 mls from 0 to 0.3 m/s. The repeatability for these larger pipe sizes is quoted as ± 0.3% of flow for flows above 0.3 m/s. The electronic package of the flowmeters is typically capable of operating in an ambient temperature of between -30°C and 55°C and the temperature limits on the process are from 0° to 84°C (Sparling Envirotech). The accuracy limits quoted for clamp-on flowmeters are usually somewhat Wider, reflecting the greater uncertainties present in such a device. The typical quoted accuracy for such a device employing a leading edge technique is ±1 to 4% of act u a 1 flow for a nom ina I pip e s i z e, wa lIt h i c k ne ss, in specified material for velocities above 1 ftls in non-aerated 1 iqui d s , wit h a z e r0 s tab iii tY a f 0 • 0 1 5 ftis. (Co n tr0 lot ron Corporation). Removal and re-application of the sensors has been found in calibrations made by Barker and Brumer to cause err 0 rs 0 f up t0 ± 5% in f I owme t e r -s ens i t iv i t Y • Ad d i t ion a I sou rce S 0 fer r 0 r inc l u d in g pip e wa I I th ic k n e S s, i n t er n a I d i arnete r , acoustic velocity in pipe wall material, and transducer axial separation have been identified by Brumer. Poor coupling between the transducer and the pipe, and misalignment of the transducer with respect to the pipe axis can cause errors as can the in tern a I sur f ace can d it i:en. 0 f the pip e •

~

p,

II-56

j

(2)

Doppler

flowmeters

Doppler

flowmeters

provide

the necessary

and

suited

are

solid the

frequency

to measurements

particles

interfaces

employ

or gas

to scatter

transmitted

bubbles

scatterers shift

in the flow

of the ultrasonic

in liquids

in which

to provide

the necessary

the ultrasonic

signal' undergoes

beam.

The

two Doppler

the configuration shown in Fig.3.10 the received signal is given by

and

for

v c

- --cos

beam

there

are

frequency

shifting

of

oprations

the frequency

81)

of

(3.11)

is the velocity of sound in the medium is the ve Ioc it y of the scatterer 81 and 62 are the transmission and receipt ion angles and respectively. The Doppler shift, fd' is thus given, by

where

U

of

c v

fd

=

fr - f

Fig. 3.10

t

= f t · ~c (cos 81 - cos 82)

Principle

of Doppler

(3.12)

flowmeter

Fig.3.1l shows an industrial Doppler flowmeter with its associated electronics. If all the scatterers are moving with the same velocity then the Doppler shift, fd' is given by

v

(3.13)

For a flow of 1 mls in a medium for which the velocity of sound is 1500 mIs, the Doppler shift is 563 Hz if the transmitted , II-57

frequency 65°

is 1 MHz

to the flow.

and

the beam

Application

is transmitted

of Snell's

at an angle

of

Law of refraction

gives (3.14)

where sound

8w is now the wedge angle and Cw is the velocity in the wedge, Le. fd is independent of c.

of

Demodulator

Fig. 3.11

Industrial

Doppler

flowmeter

In genera 1 the Do pp le r sh if t 0 f the .tran sm itted s ign a I will not be a single frequency but will consist of a band of frequencies with a spectrum as shown in Fig.3.12. The spectrum

received spectrum

transmitted spectrum

ft

Fig. 3.12

Frequency

spectra

frequency

of Doppler

shifted

signals

obtained depends on such factors as velocity profile effects, the distribution of the scatterers,the attenuation of the ultrasonic beam, non axial flow components such as turbulence II-58

and

the

transit

The shown

electronics

in Fig.3.11

is mixed

with

usually signal The

which

received

frequency fixed

u

of scatterers.

for an industrial in which

the Doppler

by adventitious

occurs

between

signals

are

is made

be shown

by means

monostable that

such

flowmeter

are

shifted

received

signal

and

the usual a zero time

a system

frequency

1)

and

estimate crossing

In

of the Doppler detector

crossing

a measure of

is

the receiver.

demodulated.

a zero

gives

- this

of the ultrasonic

transmitter

amplified of

frequency

leakage

the

every

to the r.m.s.

Doppler

transmission

flow measurement

width

proportional

effect

the unshifted

achieved

industrial

may

time

firing

a

occurs .. It which

the Doppler

is spectrum.

Limitations and accuracies of Doppler flowmeters Some of the difficulties and tlmitations which occur when Doppler systems are applied to industrial flow measurement are I ikely to occur since: (i) the nature of the scatterers, thei r size distribution, and their spacial distribution in the flow is likely to be unknown; (ii) the attenuation of the ultrasonic beam and consequently the weighting of the ultrasonic beam is uncertain; (iii) although the Doppler shift is independent of the velocity of sound in the liquid the volume which is being viewed by the flowmeter alters as a consequence of the change in an g leo f the beam inth eli qui d ; (iv ) i n 1 a rge pip e s i zest he velocities which are being measured will tend to be very close to the wall and the velocity which will be measured in either turbulent or laminar flow conditions will not correspond to the mean flow and its relationship to the mean flow is unlikely to be known and wi II va ry from 0 ne sit u a tion ta an 0 the r; (v ) the velocity of the scatterers is not the same as the velocity of the fluid. The accuracy of Doppler flowmeters is thus usually rather low. Such devices do, however, have a high repeatability in a given situation. Cousins claims that for a flow range of o to 15 mls a repeatability of ± 1% of F.S.D. can be obtained and that for small pipes with well mixed slurries a linearity of ± 2% is achievable for Reynolds numbers above 105• For large pipe size it is claimed that the accuracy is more dependent on pipe size and R~ynolds number. Doppler flowmeters have the II-59

advantages pipe

that

and

that

they

of up to 120°C {3}

can be clamped

are cheap.

and at pressures

Correlation

flowmeters

introduced between

disturbances

two stations

to estimate

estimate

of naturally

operate only

the

occurring

in the

time

shown

of the

at temperatures

by the pipe work.

flowrate

by measuring

or deliberately

form of eddies

in the pipe

the transit

can

limited

flow measurement

time

on to the outside

They

Correlation

the transit

used

they

or discontinuities

in Fig.3.13.

between

the

The method

two stations

is

the disturbances at the two points and this depends for its operation .... on the perSistence of the distribution of the disturbance within the pipe as the liquid flows between the two stations. These disturbances or noise signals can be in the form of thermal or optical noise caused by changes in the temperature of the fluid or changes in its optical density or reflectance, or they can be changes in the electrical impedance measured between two electrodes-at each station in the flow. Ultrasonics are commonly used as the method of detecting the disturbances (Coulthard, Fell). The ultrasonic transducers have the advantage that they can be placed on the outside of the pipe. The cross correlation function Rxy(T) is given by to perform

cross-correlation

I im T-+oo

lfT T

on the signals

x(t - r l v y l

t

generated

Lv d t

by

(3.15)

0

The cross correlation function Rxy(L) will have a maximum value given by Rxy(Tmax) as shown in Fig.3.13 and an estimate of the flow velocity can be given by v d where d is the Tmax separation between the sensors. The correlation may be performed using analogue or dLgital tee hn ique s. S eve ra 1 schernes are ava i Ia b Ie for per form i ng the cross correlation using microprocessor systems. (Coulthard and Keech, Henry). A review of correlation techniques has been given by Beck.

I 1-60

c

CROSS CORRELATOR

Rxy (r)

T

Fig.

3.13

Cross

correlation

3.5

~

flow measurement

Variable Area Flowmeters Df f f e ren t ia l pressure devices such as orifice plates or venturis are constrictions of fixed area across which the pressure drop is measured. Variable area flowmeters employ some method of varying- the cross section through which the flow passes in order to maintain constant pressure drop across the cross section. An element within the flowmeter changes its po sit ion wit h the f 1owme te r. to- pre sen t the f Iow wit h a va ryin g c.r 0 ssse c t ion. Th isea n be achi eve d by me an s 0 fat ape red tub e and float meter, a cylinder and piston meter, or an orifice and plug meter. (Miller). One of the most commonly used forms of variable area flowmeter is shown in Fig.3.14, a tapered tube and float meter. A feedback mechanism ensures that the float is positioned in the tube such that there is a force balance on the float between the differential pressure across it caused by the flow together with the buoyance force acting on the float, and the gravitational force on the float. Any imbalance between the forces will cause the float to move upwards or downwards.

I 1-6 1

crosssectional

areas~

gravitational

_l

velocities

--~

I

vfa

t

Aa float

force caused by diff. pressure across float due graduations

PH : volume

cross sectional area Fluid:

density

buoyancy force Vfl- .Pt..·g

Vf t

At 1

Aa .vfa = At .vft

q Aa Afl VfI PfIPr g k

q

f rom force balance and coniinuit y ~

q

= (2.Vil:9

4~

J pfI-,of • ,of

Aa

Va ria b 1e are a fIowrnete r

Ass hown i n Fig. 3.14, the b a 1an ce g i ve sri set defining equation of the flowmeter as

where

=

I'f

Fig. 3. 14

q

balance ~ float

vfo· ,..ot12

continuity: density

t

force

to How:

Aft·

Float:

force

Vfl .,Pn·g

0

the

(3.16)

k

is the flowrate is the cross sectional area of the annulus at which equilibrium will occur is the cross sectional area of the float is the volume of the float are the densities of the float and fluid respectively is the acceleration due to gravity is a constant introduced to provide correction the factors neglected in the'simple analysis.

r-

for

If Aa is made proportional to the height of the float in the tube then the flowmeter will have a linear indication. Furthermore, if the tube is constructed from glass then the float level can be read by eye. In cases where, from process

1I-62

considerations,

the tapered

tube

is constructed

of metal

the

p o s i t i on of the float can be de t ec t e d by electromagnetic

means. are required for

This technique is also employed when signals control purposes. ,Suc h f 1 O\VIIle te rs are r e lat i v 1 y simp 1 e and can be use d for the measurement of a wide range of liquids and gases. They can operate at pressures typically up to 3.5 x 106 Pa and at temperatures up to 350°C. Gas flowrates of up to 0.5 m3/s and liquid flowrates up to 0.1 m3/s can 'be measured. Accuracies of order ± 1% of upper scale value can be achieved with a rangeability of 10:1. Correction factors for density and viscosity should be applied should these change from those for which the flowmeter was calibrated. Variable area flowmeters show little effect from upstream piping conditions. Vortex Shedding Flowmeters These flowmeters depend for their operation on the fact that as flow passes over a bluff body it is unable to follow the contours of the body and flow separation from the body occurs. This results in vortices being shed from the body alternately from each side of the body and the generation of a Von Karman vortex' sh~et as shown in Fig.3.15. This is a phenomena which causes a waving of the flags in the breeze and the singing of telegraph wires. 3.6

Von Karman

Fig. 3.15 The Strouhal the free velocity

Vortex

number, in that

shedding

S, relates

11-63

Vortex

Sheet

flowmeter the shedding

frequency

to

S

where

fsh hb vf

fsh·hb

{3.17}

vf

the shedding frequency is the height of the barrier i s the free velocity. is

Linearity of the flowmeter is thus ensured by constancy of the Strouhal number and it has been found that the shedding frequency is directly proportional to the free velocity over a wid ere g ion 0 f f Iow , ex c ludin g the Iam ina r reg ion. Th era nge of operation of a particular bluff body and its linearity are dependent upon its shape, triangular or T-shaped bodies being those most commonly used. (Burgess, Miller et a1). Detection of the pressure or velocity variations caused by the vortices is by means of ultrasonic, thermal or pressure sensors. Vortex shedding flowmeters have no moving parts, provide less obstruction to the flow than an orifice plate, and are not particularly susceptible to wear. They can be used for the me asur ernen t 0 f 1iqui d san d gas e san d sin ce the S tr0 uh a I number is independent of the density of the fluid being monitored they maintain their calibration factor whether being used with liquids or gases. For Reynolds numbers greater than 104 they can provide an accuracy of ± 1% of reading over a range of 20:1. Vortex shedding flowmeters with operating temperatures of up to 20QoC and operating pressures of up to l04kPa are available.

1I-64

c_

Chapter

4

TEMPERATURE MEASUREMENT

4.1

~

~

The Concept of Temperature and the Thermodynamic Scale In his 0 pen ingad dres s tot he 19 7 I Wa sh ing ton Co n fer en ceo n 1ITemperature its Measurement and Control in Science and Industry", Preston-Thomas told a story of a previous conference during which a delegate was interviewed for the local TV station. "Now tell me Dr 'X"', said the interviewer "in simple words that a layman can understand, just what is temperature?" This was followed by a long and total silence during which the scientist was clearly trying to find an intelligible answer to the question. Without numerical systems we can rank bodies by degree of 'hotness' (simply by touching them for example) and could construct an arbitrary scale (like Moh's scale of hardness) assigning an unknown temperature a pOSition between two defined standards (hotter than melting ice, but cooler than a human body for example). We step from this concept to that of 'heat' as a measurable quantity which flows from the hotter to the cooler body. This was the state up to the beginning of the 17th century when the first liquid in glass thermometers were constructed. These, however, had quite arbitrary scales and a further century elapsed before the use of the ice and steam-points as 00 and 100 o . (0 rO° and 80 0 0 r 32 0 and 2 12 0) bee arne corrmon . Some experiments on air thermometers at the start of the 18th century hinted at the existence of a lowest possible temperature. The concept of heat as a form of motion and temperature as a measure of the intensity of that motion became acceptable in the early nineteenth century and work on steam engines had shown a direct relationship between work done and heat absorbed. Kelvin eventually put all of this together and defined 11-65

the absolute heat

engine

provided Q2

and

scale working

of temperature between

by the source these

quantities

temperatures

is Ql and are

in relation that

related

to a reversible

Tl and T2, delivered

The

heat

to the sink

is

by: (4. 1)

T2

Q2

(note that Tl is higher and the efficiency

than T2)

of the engine

is clearly: (4.2)

Numerical values are obtained by defining a single fixed point. This is chosen to be the triple-point of water which is fixed at 273.16K by definition. In principle then an unknown temperature could be determined by measuring the efficiency' of a reversible engine working between the unknown temperature and the triple-point of water. In practice this measurement cannot be carried out, but gas thermometers with very low gas-densities approximate very closely to the requirement for a thermometer working on the thermodynamic scale as do a few other instruments. None of these techniques is usable as a way of making actual practical temperature measurements or even as a means of routine calibration of practical thermometers, This is not only because the methods are complex and cumbersome, but also because they are not capable of adequate accuracy and precision for industrial and scientific temperature measurement. 4.2

The International Practical Temperature Scale (IPTS) Because the ThermodynamiC scale is not usable directly, a Practical Temperature scale is used based on the temperatures a t wh ich we IIde f.i ned chan ge s 0 f S tat e 0 f pur e rnat e ria Iso C cur • National standards laboratories in -v ar i cu s countries determined these temperatures as accurately as possible on the thermodynamic scale and then, for the sake of certainty and uniformity assigned them values which form the fixed points of 11-66

the IPTS. recent

These

version

Table

are of the

1

tabulated IPTS

Defining

in (Table

1) below

for the most

- that of 1968.

fixed points of the IPTS-68

Equilibrium state

Assigned value of International Practical Temperature

Triple point of equilibrium hydrogen. Equilibrium between the liquid and vapour phases of equilibrium hydrogen at a pressure of 33 330.6 Pa. Boiling point of equilibrium hydrogen. Boiling point of neon. Triple point of oxygen. Triple point of argon. Condensation point of oxygen. Triple point of water. Boiling point of water. Freezing point of tin. Freezing point of zinc. Freezing point of silver. Freezing point of gold.

17.042

.-256.108

20.28

-252.87

27.102 54.361 83.798 90.188

-246.048 -218.789 -189.352 -182.962

273.16 373.15 505.1181 692.73 1235.08 1337.58

0.01 100 231.9681 419.58 961.93 1064.43

These temperatures are highly reproducible (to thousandths of a degree in most cases) but they may not co-respond to their temperature on the thermodynamic scale that closely. For example, the scatter of results used in assigning the temperature of the gold point was a substantial fraction of a degree and on the basis of these results the figure was increased by about 1.4 degree from the 1948 scale to the 1968 scale. Very accurate gas thermometry may now be indicatng that the steam point (which has been taken as 10QoC for 200 years) may be in error and in some future revision we could have a steam point at (say) 99.97°C. Between the fixed points particular devices are used as interpolation instruments. Thus between 13.81K (-259.3'4°C) and 903.905K (630.755°C) the interpolating instrument is the platinum resistance thermometer, from that temperature to 1337.58K (1064.43°C) it is the platinum 10% rhodium/platinum thermocouple· and above this last temperature the scale is defined in terms 11-67

of the Planck

radiation

In practice

any

law.

reference

to a temperature

in whatever

is normally assumed to mean temperature as defined by th IPTS. In particular, expressing a temperature in Kelvins does not imply that the temperature is measured on the theoretical thermodynamic scale unless this is specifically indicated. For most practical measurements for control purposes the distinction is unimportant except that, since the IPTS is revised from time to time to bring it more closely in line with the thermodynamic scale, it may somet imes be necessary to check whether a particular measurement was made before or after a change in the scale. Thus a thermocouple calibrated at the gold-point before and after the change from IPTS 48 to 68 would appear to have drifted by 1.4K, s imp Iy because of the ch an ge in scale although the emf from the thermocouple at the gold-point might have been identical in the two tests. units

(K, °C, of, "R etc)

4.3

Dissemination of the Temperature Scale The IPTS is maintained by certain national standards laboratories (NPL in this country) and by the Bure~u International des Poids et Mesures (BIAM) in Paris. These laboratories calibrate suitable instruments supplied to them against the IPTS and supply calibration certificates for them. In particular laboratories of the British Calibration Service (BCS) have thermometers which have been calibrated by NPL and against which they calibrate industrial and other thermometers. 4.4

Types of Thermometer

(I)

Expansion thermometers The oldest form of thermometer and still the most common in everyday use is the mercury or alcohol in glass. ~ile of no dir~ct use in control work they cover a very wide range of temperatures, from say -80°C to 50QoC with high accuracy and can, therefore, frequently be used for routine calibration of control devices. Some expansion devices are used in control applications, 11-68

Gr

mercury the most bellows

in steel, common

vapour since

or shaft.

a potentiometer electrical

they

This

these they

are

because

are

simple

and vapour

bimetallic

capable

of moving

operate

system

devices

a diaphragm,

electrical

with

being

either

contacts, an

output.

devices

thermometers

The

are all

in turn may

or a pneumatic

they

and

or a forcebalance

Although

in alarms

pressure

may

still

be

fitted

and

losing

ground

to electrical

in considerable

self-contained,

may

numbers often

and,

be used

trips. pressure

thermometer

is particularly

useful

in

temp era tu r.e sin ce the pre s sur e (P) of a vapour in contact with its liquid varies exponentially wit h ternpera t u re (T) • i•e • appro x irnatel y as: de ali ng wit h n a r row

P

ran g e s

0

f

(4. 3)

= a Tn ex p (- ~~ )

where a is a constant; n is the difference between the specific heats of the vapour and liquid in units of R the gas constant; Lo is the latent heat of vapourisation. In practice, a very rough approximation is that the vapour pressure wil double for a 10°C rise in temperature.

N,

Note that the vapour pressure in the system will be that corresponding to the temperature of the liquid-vapour interface. If the temperature of the measuring bulb should pass through the ambient temperature the pressure sensitive read-~ut device will change from being full of gas to being full of liquid; the location of the interface may therefore change, and an error may be introduced by the hydrostatic head of the liq ide Special designs are therefore required for instruments working near ambient temperature. The scales of vapour pressure thermometers are ighly non-linear and there is, therefore, usually a distinction between the total temperature range and the usable temperature' range of a particular instrument. (2)

Thermocouple thermometers This is not the place to go deeply into the theory thermoelectric effect which is in any case imperfectly 11-69

of the

It may understood. metals are connected

be sufficient

to consider

that

if two

one end, as shown in (Fig.4.1) a potential difference may be measured at the open ends when a temperature difference exists between A and B. This results from the difference in work functions at the hot and cold junctions, and from the potential gradient which must accompany a temperature gradient in a conductor. together

Fig. 4.1.

at

Thermocouple

Almost any pair of dissimilar metals could be used to produce a thermocouple, but a limited number have achieved a degree of international acceptance. It should very rarely be necessary to use couples outside Table 2 in normal industrial work. Table Type

2

Types

of thermocouples

Composition

Normal Operating Range

Maximum 'Spot' Reading

E

Nickel-chromium/ Copper nickel or Chromel/constantan

-200°c to 850°C

11000C

J

Iron/copper-nickel or Iron/constantan

-200°C to 850°C

11000e

K

Nickel-chromium/ Nickel-aluminium or Chromel/alumel

-200°C to 1100°C

13000e

T

Copper/copper nickel -250°C to 4QO°C or Copper/constantan

B

Platinum 30% Rhodium/ Platinum 6% Rhodium

ODC to 1500 °C

1700°C

R

Platinum 13% Rhodium! Platinum

O°C to 1400°C

1650°C

S

Platinum 10% Rhodium! Platinum

DOC to 1400°C

1650°C

I 1-70

50QoC

r

These

thermocouples

standards

laboratories

have ~nd

recently

revised

been

studied

emf/temperature

at various tables

produced. The

difference

are usually The

small

difference

but may

the older

between

(Type

T).

these

BSI

be significant

can be as much

copper-constantan differences

between

new

as 4°C There

and

in accurate

in the case

are

tables

tables

also

and

the new work.

of

significant

the older

NBS tables

for precious metal thermocouples. The tables also include polynomial representations of the emf-temperature relationship for use in computer data-processing. These polynomials need to be treated with caution; they contain up to 14 terms expressed to 11 significant figures and cannot be truncated to obtain a lower precision representation. Dr.Coates of NPL has published some alternative forms based on Chebyshev polynomials which are much easier to handle. The important feature of the thermocouple thermometer is that it always measures the difference between one temperature and another. The position of t.h e reference junction (usually called the cold junction) is not always obvious but it must be defined for accurate work.

Reference junction Fig. 4.2

Thermocouple

Measuring Iris tr ume n t

with reference

junction

In Fig.4.2 the position of reference junction is clear and its temperature may be controlled by irrmersion in an ice-bath or some other region of known temperature. Note however that if the me asuri ngin s t rume nth as cop per wi r ing, the rea re two more junctions at that instrument's terminals - there must be II-71

no temperature

difference

between

these

terminals

if

accurate

measurement is required. In Fig.4.3 we have a less clear situation:

B

Measuring instrument Fig. 4.3

Directly

connected

thermocouple

There is no clear reference junction - in fact it is at the instrument terminals and the instrwnent will, unless it has internal compensation, measure the difference in temperature between the hot junction and its own terminals. In Fig.4.4 a cold junction is provided encompassing both legs of the thermocouple and permitting the use of copper wire back from this point to the instrument. This arrangement is particularly appropriate in scanning and logging applications, since a large number of thermocouples may all have their reference junctions in the same temperature controlled zone with the wiring to the scanner being entirely of copper. B

r----~ I i

,

I

~~========~~~~~DZ~~~ I I 1 I L __ ~_~

Temperature controlled zone Fig. 4.4

Thermocouple

with

Measuring instrument

local reference

11-72

junction

In practice, deflection instruments may have bimetal strips to move the zero of the pointer to compensate for ambient changes while electronic instruments may use resistance thermometers in bridge circuits to provide a signal for cold-junction compensation.

r--

\.__)

In industrial practice one can seldom use the same wires all the way from the measuring point to the indicator and ex t en si o n leads or compensating leads may be required. The forme r are 0 f nom i. na I1y the sarne rnate ria 1 as the the rmo C0 upIe, while the latter are alloys having a similar emf-temperature relationship to that of the thermocouple over a limited temperature range. The main application of compensating leads is with precious metal thermocouples where the high price of platinum alloys makes their use essential. As each batch of wire is made to specified tolerances on its emf-temperature relationship, the various joints inevitable in a long run of cable introduce errors in the total emf measured and these must all be evaluated in any erro analysis. An excellent manual on thermocouples is published by ASTM note however that the thermocouple colour codes shown are U.S. standards and different codes are used in the U.K. and in Europe. The life of the thermocouple depends on the type, the temperature of use, the immediate environment of the thermocouple wires and their diameter. Long life and very good stability are features of the precious metal couples provided that contamination from iron vapour is avoided at temperatures above 50QoC. For base metals used close to their upper temperature limit, a life of a few thousand hours can be expected. Base metal couples have a typical tolerance on the em f - temp era tu rere 1a t ion ship 0 f ± O. 75% 0 f Ce 1s ius t ernep rat u re or ± 2.5°C, 'whichever is the greater, and no significant improvement on this is likely to be possible in industrial conditions. The thermal history of the thermocouple and temperature gradients in the wiring can influence the emf .. If accurate calibration is required it is often best done in situ, using 11-73

a different Cycling

form

of measuring

a base

metal

calibration

shifts

temperature

gradients

instrument

couple

above

of a few degrees. may

be

alongside about

The

illustrated

800°C

sensitivity

it. can cause to

by a calibration

on a

type K thermocouple

performed at NPL at 400°C. This measurement was done first in a furnace and then in a liquid bath, and the results differed by about SoC. A new and promising thermocouple has been developed in Australia called "Nt s t lvNt c ro e i l" which is similar to a nickel-nichrome couple, but the two limbs contain a small proportion of silicon which oxidises on the surface to give a self-passivating layer, largely eliminating drift through oxidation and hence inhomogeneity. Thermocouples in swaged mineral insulated cables are generally less affected by inhomogeneity problems than units fabricated from wire and ceramic insulators. (3) Resistance thermometers These divide int6 two main types: thermistors, which are u sua 1 1 y sin t ere d mix tu res 0 f me tal 0 x ide s wit h the characteristics of a semiconductor, and units based on the change in resitivity with temperature of pure metals or alloys (see Fig.4.,S). Thermistors are not yet in common use in industrial measurement and control, although they are widely used in 1 abo rat 0 ry wo rk . Th ere a son s for t his d iff ere n cerna y be f0 un d in their highly non-linear characteristics and the lack of standardisation of their resistance-temperature relationships. They are, however, capab~e of good stability and particular rnan u f act u re r s w ill 0 f fer un its in t e rchan g e ab 1 e wit hot her S 0 f their own manufacture within a fraction of a degree. A particularly good book on thermistors is entitled "Semi-conducting temperature sensors and their applications". Temperature detecting elements based on the change in electrical r e si s t l v i t y of pure metal wires have a long history, having been proposed by Siemens in 1871 and having been used by Callender for work of the very highest accuracy in 1886. I tis only comparatively recently, particularly in this country, that 11-74

5-0

Nickel

4-0 I

ctlc?

Thermistor

/

-

o ~ LLJ

~

z·

f-!

C/)

o:

~ 1-0

u -2:Z>

~

.2'a>

~

S:::o

.iV

TElvlPERATURE °C

Fig. 4.5

Resistance-temperature various materials

curves

for

they have been used in really large numbers in industrial practice. Copper is, of course, an obvious candidate as the sensing material, since it is readily available in fine wires of high pur itY . Its us e , tho ugh, is 0 f ten con fin edt 0 specia 1 pu rp 0 se or laboratory instruments because of its susceptibility to corrosion and oxidation. The low resistivity of copper also means that very long lengths of fine wire are needed to produce a useful resistance; the result is that a copper resistance thermometer is normally rather bulky. But for some purposes it has one considerable advantage in that its resistance temperature relations ip is the most nearly linear of common pure metals. Its low cost has led to its use in some non-critical but large-scale applications such as car radiator temperature sensing systems. It is also used in long thermometers used to measure average temperature in oil tanks. Nickel

is frequently

used, particularly

11-75

in the United

States,

in temperature

coefficient

detectors.

of resistance

at room

it's resistance-temperature temperature. can

The

be corrected

associated

It has

curve

non-linear

temperature increases

resistance

using .additional

bridge

networks,

a high and

with

the slope

relationship

components

outputs

of

rising

temperature

passive

to give

temperature

in

linear

with

temeperature. Its resistivity smaller

devices

oxidation

shape

neighbourhood

The

of the resistance

is little

its wider

majority extreme

of copper,

are

still

temperature

permitting

problems limit

is set by

curve

in the

at 358°C', and by the when

it is cycled

or no international

relationship

with

instability

through

this

agreement

on

for nickel

and

this

has

use.

is not

subject

of environments; purity

upper

of the element

There

Platinum

there

point

resistance-temperature

hindered

that

of the resistance-temperature

of the Curie

temperature.

than

to be bui·It, but

and corrosion.

the peculiar

the

is higher

and

to oxidation

or corrosion

it can be obtained

its resistivity

is higher

in the

in fine wire again

than

of that

of nickel. It is also

capable

the British

Standard

from

to +850°C.

-200°C The

a small

industrial glass

inserted film

shows

into a metal

sheath.

is now virtually

resistance-temperature

at O°C and 138.5Q

thermometer

detector

deposited

a wide

temperature

a resistance-temperature

resistance

or ceramic

of platinum There

of covering

containing

More

onto

recent

a ceramic

world-wide

relationsip

of

range; tabulation

element

consists

the platinum detectors

have

of coil a

support.

agreement industrial

on the units - 100~

at lOQoC.

BS 1904 quotes two tolerance grades: Grade A - roughly ±O.2% of temperature in °C and Grade B - roughly ±0.5% of temperature in °e. The usable temperature range is from -200°C to 850°C but special care is needed above 500°C, mainly because of the danger of contamination of the platinum by iron vapour or by metallic elements reduced from the glass or ceramics. Stability is very good - a few hundredths of a degree change after several years at 60QoC. Measurements are made with some 11-76

c

form

of bridge

transmitter. of

lead

The is small, few

tens

The but

which

bridge

resistance.

connections is needed

circuit

must

Normal

for the highest and

can be

form

part

be designed industrial

a four-wire

non-linearity

may

current

of a temperature to reduce

practice

and

the effects

uses

potential

three-wire

lead

connection

accuracy.

of the resistance ignored

for most

temperature

purposes

over

relationship spans

of a

of degrees.

A rough rule of thumb is that the terminal

non-linearity is about 0.4% per 100°C span. Thus a thermometer covering ·O-lOO°C would have a non-linearity of 0.4% of 100°C (or O.4°C); used over the span 0-300°C it would have a non-linearity of 1.2% of 300°C (or 3.6°C). (4 )

Ra d ia t ion .the rmornetry (p y rornetry) The temperature of a body can be determined by measuring the thermal radiation it emits. In the range of temperatures covered by most applications of measurement and control the wavelengths to be considered run from the far infra-red down to the visible spectrum although work on plasma temperatures involves measurements in the ultra-violet. The spectral radiance NAb of a black-body is given by the Planck radiation equation: (4.4)

where

CI and C2 are constants,

A is the wavelength

and Qo the

unit solid angle. This relationship is shown in Fig.4.6 and it is this equation which, with a specified value for C2 is used to define the IPTS above the gold point.' The other constant does not require definition since the temperature scale is defined by the ratio of the spectral radiances (both measured at the same wavelength) of a black body at a temperature T and at the melting point of gold. All types of pyrometer use the curves of Fig.4.6 although in different ways. Thus a Total Radiation Pyrometer attempts to measure the total area under the curve relating to the 11-77

temperature known

Stefan

of the source. - Boltzman

This

area

is given

by the well

Law: (4. 5)

where Nb is the total radiance

and cr is a constant.

_,t?(I.

LI.l

~

E-< _..

~ E-<

~....... ~ ....J

CZ

b

[i]

KJ

0... V'J

Fig. 4.6

Black-body

radiation

In practice such instruments tend to be somewhat slow in operation and to be limited in attual bandwidth by the lens or window material and by the detector. The latter is usally a thin film thermo~ile or bolometer and, because they use all of the available radiated power, these instruments can be used to measure comparatively low temperatures (down to -50°C in some cases'). Narrow band optical pyrometers use filters to limit the band of wavelengths passed to the detector and hence respond according to the Planck equation 4.4. Some types of laboratory rather than process control instruments, compare the radiation from a standard filament inside the unit with that from the target; equality of the two is achieved by varying the filament current. This current is then used as a measure of the 11-78

c

temperature. Two

colour

pyrometers

compare

two wavelengths

to identify

complex

and not

in conmon

be used

if

the temperature. use

the emissivity

the spectral

in process

of the target

radiances These

control;

at

evices

are

they cannot

is a rapid function

of

wavelength. The narrow band pyrometer has a particular advantage in dealing with transparent materials (plastic, glass etc.) since it is possible to choose a wavelength at which the material has high absorption and is thus opaque.

Detector

. Filter Glare Field stop stop

Fig. 4.7

Electrical connector

Pyrometer

Fig.4.7 shows a typical industrial pyrometer. In practice this may be supplemented by electronics to amplify and linearise the signal. Calibration of pyrometers is carried out using black-body furnaces at known temperatures or by means of tungsten-ribbon lamps with known relationships between the ribbon temperature and the heating current. The major problem is the wide range of emissivities of the bodies whose temperatures are to be measured. On a single material this may range from say 0.05 for polished aluminium to 0.4 for sand-blasted aluminium, and from 0.07 for polished iron to 0.79 for rolled iron. 11-79

Since front

the emissivity

of the expressions

by a change the equivalent

in gain

can

be represented

in eqs.4.4

or 4.5

at the measuring

of a black-body

around

as a multiplier it must

in

be compensated

instrument

or by forming

the part

of the surface

in question.

pro b Iem 1iesin the po s sib iii ty 0 f some 0 f the radiated energy being absorbed by fume, water vapour, carbon dioxide etc., in the atmosphere between the target and the pyrometer. This may be minimised by ~ppropriate choice of wavelength, by moving the pyrometer closer to the target (and hence possibly having to water-cool the pyrometer) or by using fibre-optic light-guides to achieve a similar result. An

4.5

0 the r

Installation

and Use of Immersion

Thermometers

(I)

Conduction errors (cold-end effect) The effect of heat conduction along the thermometer element wil I result in the temperature of the sensing portion being biased towards that at the head. The magnitude of the effect depends on the heat-transfer to the medium and on the length and thermal conductivity of the thermometer stem. Usually a rough calculation is enough to establish the likely magnitude. The length inmersed,. which causes no perceptible error, is the IIcalibrated irrmersion depthl1, while that which causes an err 0 r 0 flo Cis the 11mi n imum usa b 1e iTImers ion de p th " . Th e error may be minimised by lagging the top of the thermometer. Wh en, asis us u a lin pro ce ss con t r 0 1, the the rmome te r is mounted in a pocket (thermowell) the problem is made worse by the lack of good thermal contact with the pocket. Some improvement may be obtained by spring-loading the thermometer into contact with at least the tip of the pocket. (2)

Self-heating This applies to all types of resistance thermometer (including thermistors) and is an error caused by the heating effect of the measuring current. A typical figure for an industrial platinum resistance thermometer element is O.03°C/mW 11-80

in water

or

thermometers, 5mA would

ice. lmA

be normal

In laboratory is a typical

work,

with

measuring

for accurate

platinum

current

industrial

work.

resistance

while

up to

Check

car e f u 1IY be for e us i ng any ins trume n t us i ng a me asur ing cur.ren t

in excess of lOrnA. For thermistors the measuring currents may have to be restricted to the order of tens of microamperes. Mu ch 1arge r self -heat ing figu res w i 1I 0 ccur ins 1ow 1y mo v in g g a se s •

(3)

u

Time response It is usual to assume that a thermometer element behaves as a single lag system and to declare the time to achieve 63% of a step change as the time constant; usually measured by plunging the sensor into hot water moving at 1 mise Note that the figure obtained i& valid only in water at 1 mise In air at the same velocity, the time constant might be a hundred times larger. In water at 10 mls it might be one third of the declared value. Again the use of a pocket or thermowell may greatly increase the time constant. It is not unusual to find that a thermometer with a time-constant of a few seconds when plunged into water has this figure increased to a few minutes when tested in a pocket. (4)

Thermo-electric potentials A resistance thermometer is inevitably exposed to a temperature gradient along its length which means that any "inhomogeneity in the connecting wires will produce a stray thermo~electric potential across the terminals. BS 1904 requires that the error caused by this s urious e.m.f. shall be small compared with the interchangeability tolerance when the resistance is measured at about lmA. It is, therefore, not advisable in d.c. resistance measurement to use currents below about lmA. The equivalent problem in the extension or compensating wires of a thermocouple has already been mentioned.

II -81

(5)

Total

or stagnation

In a high higher were

than

speed

the normal

.brought

temperature

temperature

gas

flow

static

adiabatically would

the temperature

be given

temperature

to rest

sensed

(TS).

at the sensor

(TT)

is

If the gas the total

by: (4.6)

where y is the ratio of specific heats for the gas and M is the Mach No. For air at room temperature (300K) moving at Mach 0.2, this increase is 2.4°C. An ordinary thermometer will usually give a reading part way between static and total temperatures. If this error is serious, special probe designs are required. It is naturally particularly important to make this distinction in aircraft instrumentation; at Concordets maximum spee d 0 f Ma ch 2 the tot a I temp era tu rei s 170 Cab ov e the stat ic temperature, which at the cruising altitude might be -60°C. 0

(6)

Installation and vibration A thermometer element may be directly immersed in the medium, if shutting down the plant to remove a sensor for rep air 0 r rep 1acernen tis accepta b 1e, .and iff a s t res po nse i s required. It may be subject to accidental damage and will be very prone to vibration. More usually the thermometer will be mounted in a pocket or thermowell. This must be stressed to stand the line pressure and the sideways thrust of the moving fluid. One must always check for likely vibration and the effect of the mechanical 'Q' of the device causing severe vibration at the tip. Thermometer elements must be supported or spring loaded in the pockets to prevent rattling and consequent early failure. The commonest cause of vibration is vortex shedding from the sides of the probe. The vortex shedding frequency given by: f

0.2

v

(4.7)

-

d

(where V is fluid velocity

and d ~robe diameter)

11-82

should be

calculated

and compared

frequency

of the probe.

with

the

A potentially

the vortex frequency than the resonant frequency.

present

if

fundamental

dangerous

at maximum

u

11-83

lateral

resonant

condition

flow-rate

is

is greater

Chapter

5

PRESSURE MEASUREMENT

5~1

j

Introduction The measurement of pressure is probably one of the most important and commonly employed measurement in industry. This is perhaps due to the fact that in many industrial applications flow rate and fluid velocity can be derived from pressure. Pressure cannot be measured directly but can be deduced by measuring the force acting vertically upon a known area. This is the basic principle of all pressure measurement techniques. It is essentially sensed by a mechanical sensing assembly, such as a diaphragm in a pressure transducer, which presents an accurately defined surface area to act upon. The unit of pressure is pascal, Pa, and has the units of force per unit area. The engineering quantity stress has the same unit. All pressure measuring devices respond to a change of differential pressure across them. There are basically four types of measurement configurations. a. Gauge pressure, called psig, is when the measured pressure is referenced to the ambi.ent atmospheric pressure. The reading is zero when the input pressure port is vented to atmosphere. b. Absolute pressure, called psia, is when the measured pressure is referenced to full vacuum, usually a sealed chamber within the device. The reading is approximately 101.3 kPa (14.7 psia) when the input pressure port is vented to atmosphere. c. Differential pressure, called psid, is when one measured pressure is referenced to another pressure. d. Sealed pressure, called pSis, is when the measured pressure is referenced to a pressure, usually in a sealed 11-85

chamber

within

the device.

the atmospheric be possible due

to vent

to unsuitable

Although system,

pressure

UK and USA,

by bar.

to quote

the pressure

floor

in terms

the bottled The

pressure

pressure

may

where

it may

measuring

used

It is still of

as 2000

is pascal,

pressure

primarily

be not

device

an accepted

psi psi

measuring

not not

550-700

Pa, within

unit

Ib/in2

the compressed

of 80-100

air

pressure

of pressure

remains

followed

in applications

the gauge

popularly

still

sealed

environment.

the unit

the most

This

in industry

or psi,

air used

in the

and perhaps,

engineering kPa

the SI

practice

on the

shop

or the pressure

of

13.8 MPa.

instruments

can

be divided

into

two

rnai n g r0 ups. Th e fir st g r0 upar e the d irec t pre ssur e me as uri n g instruments which determine the value of applied pressure by directly calculating the force applied upon an accurately known area. Various types of manometers and dead weight testers (pressure balances) are in this group. The second group are the indirect pressure measuring instruments that are based on the use of elastic mechanical elements to which the pressure is applied. Some instruments such as Bourdon tubes and capsules are allowed to have comparatively large deflexions in order to drive dial gauges. In pressure transducers, the applied pressure is opposed by a light but stiff diaphragm whose deflexion, usually very small, is sensed by a secondary transducer such as strain gauges, LVDT, capacitive transducers and an electrical output is produced. All the devices in this group are calibrated with one of the instruments in the first group. For the pressures above atmospheric, 100 kPa, a dead weight tester is use d , for pre ssur es be 1- ow this a cal i bra ted me rcur yeo 1 umn i s used. The National Physical Laboratories has the responsibility for the maintenance and dissemination of the national standards for the pressure measurement in the UK. As the rnaj 0 r i t Y 0 f mo dern pro cessp Iant s inc rea sin g 1y employ pressure transducers with electrical output for their data proceSSing, only a limited reference will be made to the mechanical pressure transducers. 11-86

t:f

(

It will for weight have

be noticed and pressure

common

difference technique transducer

that

force

measurement,

techniques.

There

in the operating of a low range using

since

the same

the methods

is, for example,

prinCiples

strain force

is the primary

gauge bearing

input

of measurement very

little

and manufacturing load cell

and

a pressure

element.

Manometer This is a pressure gauge using a liquid column as the means of pressure measurement. The measuring principle is based on the hydrostatic pressure relationship that a differential pressure is related to the column differential ~h by the expression, (Fig.5.I.A), 5.2

IIp

=llhpg

where p is the density of the liquid and g is the gravitational acceleration. This is a linear relationship assuming p and g are constants and the accuracy of measurement is limited by the accuracy with which the differential column height ~h can be measured. This may be done visually by the use of vernier graduation or by ultrasonic means ,or a more sophisticated laser interferometry technique to achieve maximum accuracy. The latter technique is used by the N.P.L. on their long-range primary barometer. ~,

-

,I

There are basically three types of manometers, U-tube (Fig.5.1.A), enlarged limb (Fig.5.1.B) and inclined tube enlarged limb (Fig.5.1.e). The liquids used depends on the pressure to be measured. Mercury is the most commonly used liquid due to relatively low temperature expansion characteristics and low evaporation rate. For a ~h = 500 mm difference in columns the ~ pressure required is 66.7 kPa for mercury, 3.9 kPa for alcohol and 4.~ kPa for water. Although a manometer is a simple apparatus to construct and operate, it is difficult to achieve the full acc racy that i tis cap ab leo f pro v idin g ., Th ere adin g s 0 f col umn he igh t s , ~h, may need extensive corrective calculations to overcome the temperature effects on the liquid_, the tube and the supporting I I -87

structure. Any contamination its properties and influence readings

should

also

be taken

...

of the liquid of the meniscus into

F2

~

which may affect (Fig.5.l.D) on the

account.

-..F.J

~

A1

-- -1 -_. .Ah

_J

~l --

A2

B

A

Hg

~~:: -- .. --- _ ..... _. -- --

c Fig.5.l

D

Types of manometers: A. U-tube; B. enlarged 1 im b; C. inc 1 i ned tub e; D. me n iscus 0 f me rcur y and water in a tube

The measurement uncertainty of liquid manometers is generally 0.25%, however, when operated in a controlled environment with sophisticated length measuring techniques, uncertainty levels of ±O.Ol% can be achieved. 5.3

Dead Weight Tester These pressure measuring instruments are normally used in laboratories and standard rooms in industry for calibration purposes. The working principle of the dead weight tester is based on balancing the force exerted by the working fluid on a piston of known area by the set of calibrated weights. Fig.5.2 illustrates the general arrangement for a typical dead weight tes~er. To operate the instrument, the required I I -88

Dead -- weights

Pressure gauge under test <,

Hand wheel Fig.5.2

Cross

sectional

view of a Dead Weight

tester

dead weights are placed on the weight support table and the handwheel is screwed till the piston carrying the weights floats freely. The piston is then rotated to ensure that the fluid film in the piston-cylinder clearance is uniform and the friction is minimum. The pressure applied to the pressure gauge is then equal to the applied dead weight divided by the area. The fluid used is normally a mineral oil type selected to suit the piston-cylinder clearance. It is important that this oil should be free from any contrunination to avoid scoring the piston and cylinder walls. In order to realise the maximum accuracy from a dead weight tester it is necessary to make a number of corrections. These are for the piston and cylinder deformation as a function of pressure, ambient temperature and bouyancy effects on the dead weights. It is alos necessary to take into account the effect of gravi tation on the fluid, piston assembly and the dead weights according to the local g value. The dead weight testers can achieve uncertainty of measurement of 0.03% to 0.01% when operated under controlled environmental conditions. 5.4

Bourdon Bourdon

Tubes, Capsules and Bellows tube pressure gauge is constructed 11-89

of a

non-circular One

cross

end of this

the fixed

end.

and a pointer applied

sectional

tube The

is fixed

formed

along

into circular

and the pressure

free end uncoils

attached

pressure

tube

under

is applied

action

to

of pressure

to this end gives

an indication

a graduated

(Fig.5.3.A).

scale

form.

of

p~

A

t p~

Fig. 5.3

Mechanical sensing elements: B. bellows; C. capsule

A. Bourdon

tube;

There are a variety of shapes used in the construction of Bourdon tubes: coiled, spiral and helical. However,the most commonly used type is the fe' shape which translates the free and movement into angular movement of a pointer by the use of a quadrant. The shape selected for a particular device depends on the measurement range and final production costs. The 'e' shape is generally used to measure up to 6 MPa and coiled shape is used above· this range. The spiral measuring elements are normally employed for special applications. Bourdon tube type pressure gauges are constructed to measure pressures in the range of 60 kPa to 1 GPa. A well designed pressure gauge of this type will have inherent

11-90

temperature

compensation

and have

a typical

non-linearity

of

0.1% •

.Th e cap su le (Fig. 5 ~3 •C ) sornetime s c a I led an era i d , I s' constructed by joining two diaphra~s arollnd the periphery by a technique such as welding or brazing. It is generally used for measuring low pressures, up to 2.5 MPa. The diaphragms used to construct capsules may be flat or corrugated. Small deflexions of a flat diaphragm, less than half of its thickness, is linearly related to the applied pressure. However for higher deflexions the non-linearity of the flat diaphragm is improved by the incorporation of corrugations. Press re gauges based on diaphragm type construction or capsules have better temperature characteristics than the Bourdon tube types. One common use for the capsule, sealed with vacuum, in aneroid barometers as the pressure transducer for measuring atmospheric pressure.

Fig. 5.4

Examples of commercially produced Bourdon tube device (left), single corrugated diaphragm and capsule stacks (Courtesy Negretti and Zambra [Av i at ion] )..

11-91

The

capsules

may

be stacked

in order

to obtain

increased

deflexion. The

bellows

having, deep axially They

convolutions

when

pressure

are generally

pressure they

the stiffness

spring

of higher

stacked

5.5

capsule

deflexion electrical

force They

transducer

under

designed

to incorporate

a good

transducers is that

member

are usually

consists

with

Bourdon

of

position quality

the pressure

tube

device

in Fig.5.4.

pressure, over

characteristic.

and

is translated

the previously

they

need

very

a useful

light

and have

In general,

sensing

as a diaphragm,

transducer.

to produce

small

of a force

such

by a secondary

devices

bearing

are shown

arrangement

the applied

signal

pressure

response

range

of the zero

in parallel

than

sensor,

well

produced

assemblies

a mechanical

mechanical

rather

Transducers

A pressure

such

seal

a measurement

as other

factor

of a commercially

Pressure

usually

stiffness

(Fig.5.3.B).

as a pressure

the stability

It is usual

displaces

bellows.

Examples and

and have

as good

end

pressure

used

tubing,

end which

to the fixed

~en

However

thin walled

at one

as a flexible

is not

sensors.

measuring

is applied

linearity

to 100 kPa.

from

sealed

elements.

exhibit, good

mechanical

and

used

sensitive

0.6 kPa and

are constructed

The

device, whose

into an advantage

of

discussed

small

deflexion

of th~

electrical

output.

superior

frequency

the accuracy

of pressure

transducers is higher than their mechanical counterparts, mainly due to the smaller deflexions allowed for the mechanical sensor. They lend themselves readily to cost effective production methods. The manufacture of certain types of pressure transducers, such as the piezoresistive type, benefits from the high technology developed for the manufacture of Integrated Circuits. Many of the applications, once handled by the traditional pressure sensors are now handled by the electrical pressure transducers which complies easily with the requirements of the modern process control systems of today's advanced process plants. Most of these transducers can also be produced for use in two-wire systems where the output is in the form of a 4-20 rnA 11-92

c-~

current

change.

However transducers additional 5.6

it must are

not

especially designs

transducer within

pressure fixed away

bearing

Pressure

used:

a useful

very

the other.

The

popular

2. dual

There

which

last decade

are

system moves

electrode

to move

change

in the

electrode

is placed

and allowed

and need

signal.

industry.

a diaphragm

electrode,

pressure

instruments

1. single

upon

these

Transducer

has become

diaphragm

electrodes from

indicating

the automotive

is applied

to the stationary

that

to produce

Type

generally

pressure

self

electronics

Capacitance This

be remembered

towards

of capacitance

where

with system

in the middle one

two the

respect where

of the

the two

electrode between

and

the

of

the pressure applied. The capacitance is measured either by making it part of an oscillator whose frequency is modulated by the capacitance change or incorporating it into t~e Wheatstone bridge configuration. Fig.5.5 illustrates the latter method. diaphragm

and

the

fixed

electrode

is a measure

p ~

~

Vex:

o~

Fig. 5.5

Dual electrode pressure detector circuit

Exci tat ion

transducer

an

the

Capacitive transducers exhibit inherent temperature sensitivity and susceptibility .t o vibration and shock, however there are a number of designs to overcome these effects. Modern capacitive pressure transducers are produced with a sputtered film single electrode on a ceramic substrate, employing a highly stable diaphragm with integrated electronics

11-93

w

voltage output. They can measure pressures from 0.1 kPa up to GPa for special applications. The general purpose versions have a non-linearity of 0.5% with a temp era tu re co e f f ic ien t 0 f sen sit 'i v i tY 0 f 400 PPMC 1 and the specially selected devices have accuracy of 0.05% with a comparable temperature coefficient of 20 PPMK-1• to convert

frequency

Reluctive Type Pressure Transducer There are two main types of pressure transducers using reluctive elements as the secondary transducer. These are the LVDT type and the inductance type. The former employs Bourdon tubes, bellows or capsules as primary sensing element. Fig. 5.6.A illustrates a pressure transducer of this type where the deflexion of a capsule is transmitted via the core rod to the core of the LVDT which in turn translates this movement into an electrical signal. It is usual for these pressure transducers to incorporate OC-LVDT in order to minimise the external circui try needed for its operation. The inductance type utilises a diaphragm as the primary senSing element. The deflexion of the diaphragm is used to change the inductance of an electrical circuit (Fig.5.6.B). A pressure bearing magnetically permeable diaphragm is placed between two coils which are formed into an inductance bridge. The bridge output voltage changes as one inductance increases and the other decreases. Many manufacturers producing this type of pressure transducer incorporate the electronics into the transducer so that they can be excited from d.c. power lines and provide d.c~ output. 5.7

Capsule Vacuum p ....

~p

~

B

Fig. 5.6

Pressure ------par t Co i 1 s

I A

Schematic illustration of A. LVDT type pressure transducer; B. reluctive type pressure transducer 1I-94

The measurement of 0.1%

for a well

application 5.8

Force The

range designed

can be up to 35 MPa transducer

used

with

an accuracy

in favourable

conditions. Balance operating

Pressure'Transducer" principle

of this

technique

is explained,

illustrates a pressure transducer using a diaphragm as the pre ssur e sen s0 r . "Th e de f lex ion 0 f the d iaph ragm iss ens ed by the LVDT displacement transducer whose output is amplified and bsed to drive the servo actuator in order to restore the diaphragm to its original position. The current, I, flowing in this servo loop is a measure of force needed to restore the diaphragm to its original position. The voltage drop across the sensing resistor Rs is used to indicate the applied pressure. The measurement range of these devices can be up to 500 kPa wi th an accu racy' 0 f 0.05% and repea tab iii ty of 0.02%. Fig.5.1

5.9

Piezoelectric Pressure Transducer These transducers are used in dynamic measurement applications where high frequency response, up to 500 kHz, is required. A piezoelectric crystal such as quartz produces no charge when subjected to hydrostatic pressure. However a charge output is produced ~hen a force is applied to this crystal by means of a force bearing diaphragm inducing mechanical stress throughout its body. A typical piezoelectric transducer is constructed from a stack of quartz crystal disks which are mechanically preloaded between two metallic electrodes. The design may also include a charge amplifier within the transducer housing to provide a low impedance output. This is a very useful addition since the output impedance of piezoelectric crystal devices are usually very high, typically 100 T ohm. The pressure measurement range is usually up to 150 MPa although for short transient measurement of up to 1.5 TPa can be obtained with the use of specially constructed devices using lithium niobate crystal. The limiting temperature of operation for the crystal is the Curie point temperature which 11-95

~------------~ Servo actuator

l.

iRs~Pi

Fig. 5.7

Pressure transducer technique

utilising

force balance

is 573°C for quartz and 350°C for most ceramic types. However the operating temperature range for the total transducer is Iimi ted by its construct ion, usually, from 200°C down to cryogenic temperatures. Strain Gauge Pressure Transducer This is perhaps the most popular device for measuring pressure in industry. Unbonded wire straiD gauges were first used in their construction. It is now common to use bonded foil or bar semiconductor and thin film deposited strain gauges. The bonded semiconductor strain gauge technique is now almost completely replaced by integrally diffused strain gauges where a silicon wafer diaphragm which is also used as the pressure sensor, is diffused directly with donor elements to obtain s t ra in gaug e s, sornetime s calle d pie zare sis t iv e .e Iernen t s , a t defined locations. The diaphrawm is popularly used as the pressure bearing member and allowed to produce strain fields (Fig.6.8). The 5.10

. I 1-96

Tangential strain

-,

I I

£

14--

u Fig. 5.8

Strain

-3Pr2(1_V2) 4t2E

r

l

I

_

!

r

distribution

1 in a clamped

diaphragm

tangential s t ra i n j-c , and radial strain, £r' are sensed by strain gauges located on these areas. A diaphragm strain gauge designed for a specific diaphragm diameter, comprises 4 strain gauges, two of which are positioned on the tangential strain field near the centre and two positioned on the radial strain field near the edge. All strain gauges, semiconductor (piezoelectric) or diffused types mounted directly on diaphragms are positioned to detect the above strain levels . . Another type of pressure transducer makes use of a strain gauge force transducer as a displacement sensor to sense the deflexion of a diaphragm to produce an electrical output (Fig. 5.9). A connecting rod transmits the deflexion to the force tran.sducer, usually bending beam .t y pe with stiffness much lower than the diaphragm, and may have metal foi 1 vacuum de po s Ited thin film strain gauges connected in a ~eatstone bridge configuration. A typical electrical circuit diagram for a strain guage pressure transducer is the same as for a load cell with the same compensation and calibration resistors. In this group, a wide variety of pressure transducers are produced to cover measurement ranges from 20 kPa to 250 mPa. j

11-97

Bending

beam

P~ Strain

Fig.

A

5.9

typical

have

Pressure transducer type load cell

transducer

a temperature

5.11

Other

The plate,

change

exploited

to a thin,

magnetic

field

pressure

and a current

to this

current

to sustain

oscillation

is a measure

civil

applied

repeatability. linearity to 0.04%

(2)

and

applied

-transducers.

50-100 PPMK-l

is passed

force

A typical

through

device is

in a The

it.

amplified

and

The -frequency applied

or

of which

is located

is detected,

of the

wire

to it can be

the centre

The wire

emf fed back of

to the wire

this or

to the diaphragm. are

u~ed

applications, A well

in aerospace, and can have

designed

temperature

transducer

compensation

oceanography

and

excellent

will

circuitry

have

built

to achieve

in up

accuracy.

Potentiometric This

of

of a vibrating

its oscillation.

transducers

engineering

zero

and Transducers

of force

diaphragm,

taut wire.

to the wire

These

frequency

sensing

attached

the pressure

of 0.25 - 0.1% and

and

Methods

as a function

to construct

due

beam

of -20°C to +50°C.

of resonant

etc.

of span

bending

type

a pressure

induced

an accuracy

Measuring

wire

tube,

employs

range

Pressure

Vibrating

have

coefficient

in the operating

(1)

wil

employing

gauges

pressure

transducer

is one of the earliest

lI-98

pressure

transducers

developed.

It comprises, mechanical Their

output

vol tag e and

basically, pressure varies

a resistive

sensor between

such

potentiometer

as a capsule

0 and

100%

driven

or Bourdon

of the applied

by a tube.

excitation

h ighie vel 0 u t put t ran sdu ce rs an indicator without the need of complicated

the y are

i nher en't 1 y

and can drive electronics. A capsule is used for the low range devices, for the high ranges Bourdon tube is employed in conjunction with a Single or multi-track potentiometer. In some transducers nonlinear tracks are used to compensate the nonlinear nature of the mechanical sensors or to provide a linear output with nonlinear change of pressure such as in altitude meters. The commercially available transducers of this type will have a range of '100kPa to 50 MPa. (3)

Resistive pressure transducer Certain conductive materials change their electrical resistance when subjected to hydrostatic pressure. This property has been utilised to construct resistive pressure transducers whose output resistance change is directly related to the pressure. The.suitable materials are carbon, zfrconium tetrachloride and manganin. The latter, an alloy of eu, Mn, and Ni is the most commercially used material and it is manufactured in the form of a bondable strain gauge pattern, manganin gauge, and usually produced by strain gauge manufacturers. Manganin gauges change their resistance linearly wit h pre ssur e and have a ty pic a I sen sit iv i t yO. 0·027 0 hm/ 0 hm/ 100 MPa. They are used to measure very high pressures, up to 1.4 GPa and to study high pressure shock waves up to 40 TPa since their response time can be as low as a few nanoseconds. (4)

Novel pressure techniques

transducers

and pressure measurement

There are a number of novel pressure transducers that have been either cited in literature, or used for research purposes or only available conmercially for special applications. A selection of these are listed below: 1. Use of Hall effect devices to measure deflexion of a 11-99

pressure

bearing

2.

sensing

3.

dr iv i ng of angu 1ar encoder' by Bourdon

4. 5.

6-. 7.

of eddy

diaphragm, current

losses

in deflecting

diaphragms,

tube to produce

binary or BCD outputs, Bourdon tube made from fused quartz, use of hydrostatic pressure sensitive properties of planer transistor and a number of other crystals such as iridium antimonide, a va r i e t y 0 f m i c rornec han i ca Ide vic e s bas edon the pre ssur e sensitive property of silicon monolithic leis, resonating quartz sensor.

11-100

Chapter

6

LIQUID LEVEL MEASUREMENT

6~1

u

Introduction The measurement of liquid level is a fundamental one used in the automatic control of continuous processes. It is f re que n t IY use din. con j un c t ion wit h ·0 the r bas i c me a sur ernen ts 0 f temperature, pressure and flow for the control of processes in chemical and petroleum industries and is of prime importance in water works, power stations, steam raising plants and a number of other applications. Several principles of measurement are used in determining the level of liquids. The type of instrument selected being governed by, the nature of the liquid, the shape of the vessel in which the liquid is contained, the pressure under which it is operating, and the application. Toe nab let he va rio us ins trume n tsus edt 0 qua n t i f y the measurement made, various units are used. Linear units such as Metres for a direct measurement of depth or pressure units such as bars for a pressure head.

_)

6.2

Methods of Level Measurement Level can be measured in a number of different ways. The simplicity or complexity of the instrument used will depend largely on the application of the measurement, whether it is an infrequent measurement made for long term records or a continuous measurement. needed for the auomatic con t ro I of a complex process. The main types used in'the process industries can be grouped under the following classifications. 1. Visual Indicators 2. Float actuated instruments 3. Displacement type instruments 11-101

4.

Hydrostatic

5.

Differential

6.

Probe

methods

7.

Radio

frequency

A description and (1)

The

instruments

pressure

instruments

methods

of these

industrial Visual

pressure

types,

applications

generally

encountered

in process

follows.

indicators

simplest,

and probably

me a sur i ng 1eve 1 ina n

the most

common

method

of

pen tan k, r i ve r 0 r flume, i s byrne an s 0 f a di p s t ick or gauge staff irrmersed in the 1 i qu i d and ma r.k ed off in contents or depth over a datum line. The dipstick although crude and simple is a very accurate method of level measurement but cannot be used for automatic recording or controlling purposes. It has many applications where a continuous indication is unnecessary but where regular readings can easily be taken. A very corrmon application of the dipstick is known by every motorist when he regularly checks his oil level. 0

I

Scale

c

Vernier Clamp Taper Point

Fi g. 6.1

Hook gauge

A development of the simple dipstick is the hook used where accurate measurement of the liquid head of or open tank is required and where it is difficult to the eye wit h the 1 i qui d sur .f ace. Th i s con sis ts 0 f ash I1-I02

gauge a river align arp

pointed

hook

(Fig.6.1). raised

attached The

until

allo~ing

to a vernier

hook

is lowered

the point

the

An optical

level

into

of the hook

to be read

version

scale

off

the

just

mounted

on a gauge

liquid

and gradually

breaks

the surface,

on the vernier

of the hook

gauge

staff

is found

scale. in the

is placed pointing upwards in the liquid. This point is viewed through an eye piece at an angle in such a manner that an inverted reflection of the point is also seen in the eye piece (Fig.6.2L reflecting

point

manometer

in which

a steel point

u

Fig. 6.2

Reflecting

point manometer

The point is raised, and the level read, when the tips of the viewed and reflected points meet. This method of measurement, although elaborate, overcomes surface tension problems encountered when trying to estimate when the tip of a standard hook gauge breaks the liquid surface. Another type of visual indicator is the sight glass, consisting of a transparent tube mounted on the side of a vessel and connected to it by pipes at the top and bottom. The liquid in the tube rises to the same level as in the tank and its height can be compared and recorded against a graduated scale .behind it. Sight glasses are frequently used to measure the water level in the drum of a boi ler. Such devices, because of the high pressures involved, are constructed within a steel chamber with a thick glass opening front and back. By the use of a two coloured glass strip behind the sight glass and the refractive effect of water, a clear indication of the water level is obtainable, the space above the water line appearing blue and that below the water line, red. 11-103

These the from

liquid

methods surface.

an accessible

measurement

of

level measurement If, however,

position,

to a more

the tank

a means

convenient

require

easy

is elevated

of transmitting

position

access

needs

to

away

the

to be applied.

is to be found in the balanced float method. A float resting on the surface of the liquid is connected by a chain or wire over a pulley to a counterbalance weight and pointer which is conveniently positioned against a calibrated Such

a device

scale. (2) Float actuated instruments A development of the balanced float described above is the chain and float gauge consisting of a hollow float resting freely on the liquid surface and connected by a cord, chain or thin metal 1 ic tape over a pulley to a counterbalance weight. The float maintains a constant depth of immersion in a given liquid and rises and falls with any change in the liquid level. In so doing, it drives a pulley which operates an indicating, recording or control mechanism to show the changis in level (Fig.6.3).

Recorder

Counterweight

Chain or Tape

Float

Level of liquid

Stillingwell

Fig. 6.3

Chain and float recorder

11-104

Turbulence the

float

pulley, drive

in the

by

over

the addition which

mechanism

recording

or

installations the point

The

where

the

of measurement.

be prevented

runs,

through

indicator

scale.

can

of a stilling

the chain

which,

pen

calibrated

liquid

actuates

gears

pointer

chain

and

well

and

instrument

can

it.

instrument

a chart

operates

used

a

or

is used

be mounted

The

on

directly

over

as a river

head over a we i r or flume. This device cannot be used for applications where the liquid is under pressure. Here some method of transferring the movement of the float through the container wall would be needed. A caged float controller is used for pressurised applications (Fig.6.4). A float and lever contained in a metallic cage, which is connected to he pressurised vessel, follows any va ria tion i n 1eve I. Th i s mo vernen tis t ran sm itt edt h r0 ugh the cage by a shaft rotating in a gland or stuffing box to a counterbalance lever outside the cage. This outside lever operates.a pneumatic controller, or electrical switches or can be directly linked to a control valve regulating the flow of liquid into or out of the vessel. g.auge to record

flow

by mea sur i ng

the

gauge

It is frequently

affecting

around

linkages

against float

from

t he

I'tI[SIUltt O LA\OlN'

Fig. 6.4

Caged

float controller

(3)

Displacement type instruments The level detector, here, is a displacer, usually produced from a cy lin de r wit h c lose den d s w hie his pre ssur e t igh t (Fig.6.5).

11-105

__J:;:;"'1 -,

-

; "\ ~

Driver

__

Torque

~-\ __

___

Bearing

Tube

Displacer Rod

~ ~

Fig. 6.5

Displacement

Displacer Cage

type instrument

The displacer is denser than, and therefore sinks in the liquid being measured. The actual measurement made is the apparent weight of the displacer which reduces as the liquid level rises. The loss in weight is equal to the weight of liquid displaced, which in turn is governed by the volume of the displacer and the height of the level relative to the bottom of the displacer. The weight of the displacer is ·measured by a torsion spring known as a torque tube assembly which transforms the weight variation into an angular movement of a torque tube shaft (Fig.6.6).

Fig. 6.6

Torque

tube assembly

11-106

This angular movement can be used to drive a pneumatic or electronic transmitter or controller, producing an indicating or controlling output signal in direct proportion to the 1 iquid 1eve I_ from the bot tom 0 f the dis P Iace r . Ob v i0 U sly, i f the level rises above the top of the displacer no further change in weight takes place and therefore no further indicatio of level

u

change is possible. The total variation in level measurement is ther~fore, governed by the height of the displacer. Displacement units can also be used to measure the position of interface between two irrmi sc i b le -Liqu i d s having different specific gravities. This is commonly used to measure the interface between oil and water in a separator chamber to allow the oil and water to be drawn off the vessel individually. In this application it is essential that the displacer is always submerged in liquid. Materials used for the construction, particularly the displacer and torque tube assembly are carefully selected to combat the corrosive effect of the liquid or liquids being measured and the pressure and temperature of them, because this method of measurement like the caged float controller can be used for pressurised containers. (4)

t===~\

Hydrostatic pressure instruments These instruments measure level by measuring the pressure exerted by the liquid on the measuring element. Various me a sur i ngel ernen t s can be use d such asap res sur ega ug e , a bubble pipe, a pressure bulb or a force balance pressure transducer. A pressure gauge directly connected to the discharge line from a storage tank can be calibrated to read directly the contents of the tank or liquid head above the gauge (Fig.6.7). A bubble pipe level gauge can be used for many ty~es of liquid regardless of its corrosive nature providing a suitable mpterial can be chosen for the pipe. It is also suited for measuring the level of liquids carrying solids in sus ension. In this instrument a small quantity of air or other non corrosive gas is aI,lowed to bleed into a pipe lowered into the liquid (Fig.6.8). 11-107

Fig. 6.7

Pressure

Gauge

or Recorder

Gauge

mounted

in Pit

to record

level

gauge

~---

Gauge or Recorder Regulator Air Supply Flow Indicator

Bubble

. --

-- --

- -- -

Bubble

pipe

-

_

~

=- = ~ ;._=_ -=_Fig. 6.8

level gauge

The gauge measures the pressure of air needed to displace the liquid in the pipe which is directly proportional to the head of liquid above the lower end of the pipe. It is imperative to always have a flow of air through the bubbl~ pipe, so there is usually a flow indicator built into the system, and the pressure of air or gas needs to be controlled at a value slightly higher than that needed to balance the maximum level head intended to be measured. The only disadvantage of this

11-108

system

is that

resulting

as the

in a high

A force

In this

a diaphragm

which

and

pneumatic

exactly

balance

pressure type

pressure

the

transducer

of

to the pressure

air

utilises

is measured

liquid

increases

air.

also

level

on the other

liquid

flow

of compressed

of gauge,

is exposed the

falls

consumption

balance

p re s su re ,

level

pressure

side which

air

by means on one

is controlled

of side to

(Fig.6.9).

Q

u

o '..--r:..-L__, __

Transmitted Pressure R

, Fig. 6.9

Force balance

Supply

diaphragm

gauge

A pneumatic pressure greater than the liquid head to be measured is applied through the supply connection via an orifice 'R' to the right hand side of diaphragm 'Q' to oppose the force exerted by the liquid head. A bleed orifice '0' is provided' in the housing to vent the diaphragm chamber at a rate such that when the diaphragm is in equilibrium, the rate of air flow into the chamber equals the rate of flow out of it. Variations of pressure in the diaphragm chamber are measured by means of a pressure gauge or pressure receiver calibrated in terms of I iquid level. (5)

Differential pressure instruments The hydrostatic pressure instruments previously referred to can only be used when the vessel to which they are applied is open to atmosphere. ~ere the container is pressurised a 11-109

differential container beneath

pressure pressure

the

measurement.

liquid

Fig. 6.10

must

be made,

can be subtracted

from

surface

the actual

A simple

for this purpose

measurement

to obtain

mercury

IU'

so that

the total

the

pressure

level

tube, manometer,

can be used

(Fig.6.10)~

A mercury container

'u'

tube used with a pressurised

Here, the pressure of gas above the liquid is applied effectively to both legs of the mercury tube, so the height H of the mercury is directly proportioned to the height L of the liquid. This method enables the level to be measured at the bottom of the vessel which may be more accessible than a sight glass which would have to be viewed in line with the actual level surface. (6)

Probe methods The capacitance probe (Fig.6.11)is an electrostatic instrument measuring the change in capacitance of the probe when immersed in a liquid. The capacitance change can be measured by an electronic circuit adjusted to give level indication over the desired range. The probe usually consists of two concentric tubes where the capacitance is a function of length and diameter of the tubes and the dielectric constant of the material between the tubes. The variation in capacitance is measured and converted into direct current readings. This method is suitable for most liquids other than those which

11-110

Fig. would

separate

conductor. froth

Capacitance

on standing

It is also

excessively

deposit

into

unsuitable

probe a co~ductor

and

for conducting

or where

solids

contained

of probe

instrument

a non

liquids

in the

which

liquid

could

out.

Another one

out

6.11

type

set position

of

level

used

is the vibrating

only

to in icate

probe

(Fig.6.12).

F'lange

Magnetic Vibrator '~

Vibrating

U--------

Fig. 6.12

Vibrating

Probe

Diaphragm

probe

The probe unit consists of a detecting device, a control amplifier and the necessary interconnecting wiring and mains supply_ The probe is mounted horizontally at the required level on the tank or hop,per wall such that the fluid or granular material in the tank can come in'contact with the probe. The probe assembly consists of metal rod paSSing through and fixed in the centre of a thin metal diaphragm welded into the bore of a flange, allowing both ends of the rod free to vibrate. One end of the probe projects into the tank while the 11-111

other magnet

end

is housed

coil

assembly

outside used

the tank to vibrate

in conjunction

with

a

the probe.

tank contents is below the probe it is free to vibrate but when the level reaches the probe it is prevented from vibrating and stops the driving ~ircuit from oscillating. This, through a control relay, and amplifier circuit can initiate a control device to empty or fill the tank or it can operate an indicator lrunp or alarm device. ~ile

the

(7) Radio frequency method This method of level measurement operates by measuring the position of a small sensing element emitting radio frequency signals from an antenna which is maintained by a servo mechanism about 2mm above the liquid surface. The probe is linked to the servo mechanism by a perforated stainless steel tape and the movement of the servo mechanism provides an indication of liquid level. This method, although expensive is very accurate and is unaff~cted by liquid specific gravity and has applications on large storage tanks handling corrosive liquids either at atmospheric or pressurised condition. 6.3

Summary

(1)

Visual indicators Visual methods of level measurement are used where no direct control of the process is required and where periodic readings of the level can be made to ensure it is within certain limits. Visual methods are the most economical of all the measuring devices. (2)

Float actuated instruments Various types wjthin this range can be chcisen depe~ding on whether the liquid being measured is operating under pressure or .is open

to the atmosphere.

The

latter

types

are

limited

to

where easy access above the point of measurement exists and is typically used as a river gauge. It has the advantage that it can be linked to a recorder to enable permanent records of changes to be made. The pressurised units have a certain 11-112

~

limitation direct (3)

of span

control

may

operate remote

type

a control

valve

the point

of the

facility

of

if required.

method

for pressurised

or electric from

the advantage

instruments

is a versatile

be used

pneumatic

have

of the process

Displacement This

but

of

liquid

containers.

control or an

signal

level measurement It produces

which

indicator

may

either

be used

or recorder

which a

to

located

of measurement.

(4)

u

Hydrostatic pressure instruments Various methods in this category, ranging from a simple pressure gauge to a sophisticated force balance transducer, cover a wide range of applications. Most of these types can· be used where the liquid is corrosive, providing a suitable material for the sensing element is chosen. (5)

Differential pressure instruments The same range of devices and applications apply to this category as to the preiious one. In most instances it is accomplished by using two devices, one at the top an one at the bottom of the vessel. (6)

Probe methods The capacitance probe referred to is limited to liquid applications where the liquid remains stable and is of a conducting type. The vibrating probe is only used to indicate a particular level attainment but can also be used for granular materials. (7)

Radio frequency methods A rather expensive but very accurate method which is unaffected by the .liquid specific gravity or corrosive nature, since the sensing element never comes into contact with the liquid.

11-113

Chapter

7

CONTROL VALVES AND ACTUATORS

7.1

'--j

Introduction A control valve is a device which regulates the flow of a fluid in a pipe line. It consists of two elements, a restricting element and an actuating element. The actuating element commonly known as an actuator, transforms a control signal from a controller into a motivation of the restricting element which, in turn, regulates the flow of fluid in the pipe line. The control valve is often "referred to as the last Iink i the automatic control system, and is probably·the most important individual unit in the loop. All the effort of measuring the variable, transmitting and comparing its value with the desired value, and initiating a control signal would be waste if the control valve did not make a correction to the process, in accordance with the response corrections called for by the controller. Nobody really knows when the first control valve was produced, but there is evidence that the Romans used valves for the control of water flow. These were usually made from wood and were manually operated, so the actuators were in that case humans. The advent of the Indust~ial Revolution brought with it many instances where control valves were needed to be automatically controlled. Instead of having a hit-and-miss method of someone watching a pressure gauge or level measurement, and turning a handwheel to close a valve down or open it up, there needed to be an immediate link between the measurement taken and the 0 per a t ion 0 f the val vet 0 red u ce time 1ap se, and avoid unnecessary waste in both time and valuable process fluid. During the early 1900s, sales of petrol driven motor cars and then the advent of World War I, heralded a growth in the petroleum industry, where more control valves were needed to 11-115

maintain during

the continuous the

required

1920

more

developed, valves 7.2

to 1930 era, the basis

of the present

The Restricting pait

range

used

two categories;

(1)

Sliding

fluid

valve

screwed

To vary

which

equipment

day

range

instrumentation

was

valve

in the control stem

to be capable

which

were

of contrnl born.

is responsible

in many

industry and

forms. falls

for The

basically

rotary.

of controlling

a pipeline. body,

To achieve or has welded passage

which

can

the

therefore

flow o~ have

a

be conveniently

the valve

body

fitted

is either

connections. through

within

a seat ring ~nd a moveable

It must

this

the flow of fluid

be an adjustable

control

is available

as the valve

the pipeline.

flanged,

industries

valves

through

known

flow

sliding

has

passing

housing into

stem

Gradually

Element

the fluid

into

The

control

of the control

currently

developed.

new process process

and

regulating

being

sophisticated

and associated

This

processes

the valve,

the valve.

there

This

needs

is provided

to by

valve plug (Fig.7.1).

Packing Bonnet Valve Stem Body Valve Plug Seat

Fig. 7.1

Flow passage

through

a valve

The valve plug is connected via a stem to the actuator and therefore moves in accordance with the dictates of the control II-llB

f' <..

signal. this

The

determines

response movement

between

is very

change

movement

the flow

which

will

because

develop

of the actuator.

through

the control

important,

the valve

signal,

and

in

This

the

is referred

linear to as

Characteristics

percentage

Fig.

signal,

three

basic

and

quick

opening

Inherent

in flow whereas in control

produce

a much

characteristic

percentage

or decrease signal

when

smaller

linear,

equal

change

increase

the plug

which is close

in flow

or

in the control

characteristic

in flow,

change

curves

a proportional

incremental

the equal

used;

(Fig.7.2).

produces

for each

increase

characte~isti6s

flow

characteristic

percentage change

are

7.2

linear

decrease

will

of flow

linear

from

plug

characteristic.

There

~)

the amount

produced

the valve

The

of the valve

to a specific

relationship

1)

shape

means

produces that

to the

than would

a

a

seat, be

the same change in signal at a point where the valve plug is some way off from the valve seat. The quick opening characteristic is opposite to that of the equal percentage, producing a large change in flow for a small lift of the plug from the seat. The selection of the ideal characteristic for a control produced

by

valve depends upon the application for which the valve is being used. The installed characteristic, which is obtained when the valve is in actual use, may well be different to the inherent characteristic, since the pressure drop across the II-117

valve

producing

flow may well

change

as the opening

of the valve

changes. The level

linear

control

required.

characteristic

and

The

pressure

equal

control

the pressure

for flow

drop

opening

characteristic

2)

the valve

actuator

a large

by the system

to open

used

rapidly

liquid

gain

is used

is

on

percentage

as a whole

at the control

which through

valve.

valve

and pass

a high

of

with

The

for relief

from

frictional

known

only

quick

applications flow with

which

a special

of valves

up to 40~.

connection.

hazardous

may

occur

seal

called

and plug

size

for reduced

Here,

or very

through

loss of

with

little

expensive

the packing

a bellows

packing

prevents

to move

seal

forms

The

valve

size,

A single

of equal

flow

body

ported,

stem

denotes

the size

with

size

fluids would

be

can be used

to be kept

can

take

valve

has

one variable

valve where

to

forms. or angled,

the appearance passage

II-118

from

of the pipeline

trims, the

range that

is, the

or of a smaller inlet

velocity

low.

various

through

category,

to the body,

requirements,

straight

ported

having

size

sliding

can be fitted

is required

Body

in this

This

They

seat

water-tap,

rings,

the stem

For

box.

stem,

range

Sizes

or double

section

by the bonnet

of the valve

or packing

allows

the pressure

is achieved

movement

or square and

through

plug

the packing.

Size

the valve

This

linear

to the valve

pass

as the gland

the bonnet, leakage

must

assembly.

of moulded

undesirable, replace

which

resistance.

any

is transmitted

unrestricted

an area

in the form

where

stem,

of the body

allows

fluid

movement

the valve

envelope

4)

a constant

characteristic

is often

for

Bonnets

through

12mm

where

and where

available

needs

selected

lift.

The

3)

percentage

is absorbed

percentage

a small

control

applications

a small where

is usually

It can be single or three-way. of a domestic

to the flow

stream

to

(Fig.7.1).,

This,

applications pressures

need

the vlave

generally such

involving would

to force

up

producing through

correspondingly

a balance

direction.

valves This

valves,

in order

damage,

which

High

construction

one opening of forces

to minimise occur

the

with

the sianming if flow

to close

stream

is

the other, flow

in a 'flow

important

are

of valve, flow

through The

pressures

appl ications

construction

down

limited

high

actuator

pressure where

kept

has

because

(Fig.7.3).

is normally

is especially

would

and

sizes,

higher

by a balanced

ported

larger

low pressures,

plug closed.

through

most

in the

only

accommodated

as a double

passed

especially

direction

to open'

single

effect

ported

and

operation

consequent were

used.

u

Fig. 7.3

A double ported

valve

Three-way valves are used where two flow streams need to be mixed in variable quantities, or where one stream needs to be split into two pipelines, again with the facility to vary the amount selected for each line (Fig.7.4)., This type of valve is often used on temperature control applications .. (2)

Rotary valves In rotary valves the restricting element moves in a rotary path relative to the valve body. There are various known as ball valves, butterfly valves and eccentric disc valves. Every valve, due to the formation of turbulence, heat etc. produces a loss in pressure in the pipeline 11-119

\

\,

forms,

noise, known as

apr

e s sur e d r 0 p •

than sliding valves.

Ro tar y val ve sin g enera I cause 1 e ss res tric t io-n stem valves and are referred to as high recovery

Fig. 7.4

Three-way diverging

valves flows

used

for converging

or

1)

Ba I I val ve s These have a rotating, hollowed out ball which produces a varying flow passage, depending on its position (Fig.7.5). ~en in the wide open position, a ball valve provides negligible resistance to the flow path and therefore creates a very small pressure drop. The action of the ball when closing has a chopping effect which is very useful when handling fluids such as slurries or paper stock.

Fig. 7.5

A V-notch

ball valve

2)

ButterflY valves These have a rotating disc which rotates within a wafer body, such that when the disc is in the open position it

11-120

~/

projects

into

the pipeline

Fig.

,~

, I

7.6

(Fig.7.6).

A typical

butterfly

valve

One must ensure therefore that the valve is in the closed position before attempting to remove this type of valve from the line. The disc of the butterfly valve rotates about its centre and when closed it is difficult to achieve a shut-off condition with a very low leakage path. This problem lead to the development of the eccentric disc valve, which has a centre of rotation off-set from the centre of the. disc, allowing it to close tight against its seal ring and also having the advantage of reducing wear between the disc and the body of the valve (Fig.7.7). 3)

Size The inch) to inch) to

range sizes of rotary valves available range from 25mm (1 600rrm (24 inch) for ball valves, and from 50rnm (2 900nm (36 inch) for butterfly valves.

4) Characteristics The characteristic of rotary valves cannot be varied as they can for sliding stem valves, and approach an equal percentage characteristic for butterfly and eccentric disc 11-121

valves

and approximately

Fig.

7.7

linear

An

characteristic

eccentric

disc

for ball

valves.

valve

(3) Materials

The materials chosen for the valve body in both sliding stem and rotary valves has to be strong enough to withstand the pressures and temperatures exerted on the valve in both test and operating conditions, and must resist the corrosion and erosion effects of the flowing fluid. A large majority of control valve bodies are made from high-tensile cast iron or cast carbon steel. But alloy st~els, stainless steels and special materials need to be selected for handling corrosive fluids, or where the flowing temperature is .abnormally low or high. The valve plug, seat rings, valve stem, guide bushings and packing parts, which are often referred to as the valve trim, are usually manufactured in stainless steel, but again special materials need to be selected for very corrosive applications. Hard surfacing materials such as cobalt alloys are often applied to valve seats and gUides, and are an economical solution for services handling high temperatures or pressure drops. (4) Valve sizing It can be shown from Bernouli 's energy equation that the relation between the flow and the pressure drop across a restriction in a pipe follows a square root law. We can 11-122

therefore

state

multiplied valve.

that

the

by the square This

the sizing the Cv of

constant,

of control the valve. Cv =

flow

is proportional

to a constant

root

of the pressure

drop

the valve valves, The

Qj

technologists

and,

equation

for

liquid

used

for

use flow, liquid

across

the

to enable is known sizing

as

is:

G

i1P

Equations for gas and steam sizing are similar in construction but involve more factors and result in a Cg value for gases and a Cs value for steam. Practical tests carried out on each type and size of valve determine a usable sizing co-efficient for each valve which is listed by manufacturers for comparison. 7.3

Actuators The valve actuator is that part of the control valve which accepts a signal from the controller, and uses this signal to position the restricting element of the valve to control the fluid passing through the valve body. Different types of valve actuators are used for operating control valves. The corrmonest type in use is the pneumatic spring opposed diaphragm actuator. Other types are pneumatic piston actuators and electric actuators. A valve actuator has to operate satisfactorily in conjunction with a control valve operating in a control loop under all service requirements. There should normally be a linear relationship between the control signal and the output movement of the ac tua tor, hy s teres is 0 f movemen t mus t be negligible or kept to an absolute minimum, and the actuator must be sufficiently stiff to withstand the operating forces which arise from operating the control valve. The design must also be rugged enough to withstand the stresses encountered during shipment as well as during normal plant operation. (1)

Pnewmatic diaphragm actuators Be cau se 0 fit's simp Iicit y, the pn euma tic sp r i n g opposed diaphragm actuator is by far the most widely used type. lI-123

It is used

in conjunction

valves,

and

except

those

great

that

finds

with

applications

in which the power

both

sliding

on all

the unbalanced requ-irements

types forces

stem

and

of valve

rotary bodies,

on the valve

of the spring

are

so

opposed

unwieldy or impracticable. A typical pneumaic spring opposed diaphragm actuator is shown below (Fig.7.8). It consists of a moulded rubber diaphragm contained within diaphragm casings, and opposed by a loading spring mounted on a connecting yoke. The movement of the diaphragm is transmitted through a diaphragm plate driving an actuator stem connected to the control valve stem. diaphragm

actuator

Fig. 7.8

make

it

A typical pneumatic

diaphragm

actuator

The control signal applied to a diaphragm actuator is in the form of an air pressure, usually in the range of 0.2 to 1 bar such that the actuator stem starts to move at 0.2 bar and completes its travel at a pressure of 1 bar. D iaph ragm act u a tor s are ava i Iab 1 e i n va rio u s s i zes wh ich are selected to suit the size of the valve and the operating pressure conditions within the valve. The actuator action can be selected such that increasing air pressure to the actuator pushes the actuator stem down, which, on a push down to close valve, would result in increasing air pressure closing the valve, or it can have the reverse action, such that increasing air pressure opens the valve (Fig.7.9). The type of actuator chosen usually depends 11-124

onwhether signal the

the valve failure,

safety

Fig. Manual during

air

failure.

Valve

Two

handwheel

important

diaphragm

or handwheels a means

when

or air

considering

can

during

mounted

be

top of

fitted

to diaphragm

positioning

start-up

of handwheel

on the

actuator

of manually

the valve

or in the event

are generally the valve

on the yoke

the diaphragm

with

in propo~tion difficult

in the event

used,

actuator,

of the valve

of either

or a side

actuator.

positioners

Although designed

acting

types

mounted

or close

system.

an emergency,

a handwheel

1)

A reverse

to provide

open

can be very

operators

plug

mounted

which

of the overall

7.9

actuators

should

sufficient

actuated force

to the change

service

control

to position

sufficient

is generally

the valve

in instrument

conditions

valve

signal, force

under not

be

a valve positioner or booster relay should be used in conjunction with the control valve to ensure accurate and dependable positioning of the valve (Fig.7.10). The valve positioner is a pneumatic positioning device mounted on the valve actuator yoke with a mechanical connection to the valve stem, and operates to modulate the air pressure on the valve actuator diaphragm until the valve stem is positioned in available.

Where

such

co nd lt Io n s exist,

may

accurately

11-125

-------------------

_

-_ .. __ -.-.__ ......•. ..••.._

_

_-_ ..__ .._--_

_. __ ..

_ .

accordance

with

to a schematic operation

Fig ..

the demands of a typical

of the control valve

signal.

positioner

will

Reference clarify

the

(Fig.7.11).

7.10

A valve positioner acting actuator

mounted'on

a reverse

Rf.VEllIiE AcnOH QUAilIlAIC"I

Fig. 7.11

Schematic

illustration

of a valve positioner

Air pres~ure is supplied to the relay supply point and a fixed restriction. A flapper moves against a nozzle which is connected to the fixed restriction. The diameter of the fixed restriction is less than the diameter of the nozzle so that air can bleed out faster than it is being supplied when the flapper is not

1I-126

restricting

the nozzle.

the bellows

expands

restrict

to move

the nozzle.

a relay

diaphragm

relay.

This

allows

When The

assembly

the

instrument

the beam,

nozzle

toe output

causing

pressure

to open

the

increases

a supply

pressure

pressure

valve

increases,

flapper

to

and moves within

the

to the di aph ragm casing

of the control valve to increase, moving the actuator stem downward. Stem movement is fed back to the beam by means of the cam which causes the flapper to move away from the nozzle. Nozzle pressure decreases and the relay supply valve closes to prevent any further increase in output pressure. The positioner is once again in equilibrium but at a higher instrument pressure and a new valve plug position. When the control instrument pressure to decreases, the bellows contracts, aided by an .internal range spring to move the beam and uncover the nozzle. Through relay operation an ex h au stva 1 ve inth ere I a.y 0 pen s tor e 1 e as e the d ia Iih ragm pressure to atmosphere, permitting the actuator stem to move upward. Stem movement is fed back to the beam by the cam to reposition the beam and flapper. When equilibrium conditions are obtained the exhaust valve closes to prevent any further decrease in diaphragm casing pressure. For each value of control signal, therefore, there is a finite v al ue of valve stem position which will always be established, regardless of external force variations applied to the valve stem. (2) Piston actuators When the application is such that the valve actuator is required to operate against heavy out of balance forces caused by unbalanced pressures, or the weight of the valve, or is handling high viscosity fluids, the valve actuator is required to develop a thrust greater than that which can be conveniently supplied by a diaphragm actuator. In these circumstances, a piston actuator may be used to operate the control valve. The piston actuator is generally pneumatically operated and is either integrally mounted on the valve (Fig.7.12) or is furnished as a separately mounted power cylinder for use with large butterfly valves. The actuator consists of a double acting piston in a cylinder operating on an air supply of up to 11-127

10 bar,

through a valve positioner, signal of 0.2 to 1 bar.

fed to it

instrument

Fig. '7.12

working

on an

A piston actuator

The piston actuator relies on a difference in air pressure on either side of a piston to cause movement of its actuating stem to, str0 ke the con tr0 I val ve . As the pis ton is not sp r ing loadedan d 0 per ate sat a mu ch h i gher p r,e ssur e than that furnished by the controlling signal, it is necessary to incorporate a valve positioner in the operating mechanism to act as a relay and feedback device to control the movement of the piston and hence the valve opening. To understand the operation of the piston actuator refer to the schematic (Fig. 7.13). The pneumatic signal from a controller is fed to the bellows of the pOSitioner. On an increase in signal pressure the bellows expands and moves a beam which pivots around a fixed point simultaneously to uncover the nozzle of the air relay "B" and cover that of relay nAn. The nozzle press~re of relay nA" increases and through relay action causes the cylinder pressure over the top of the piston to increase. At the same time, the nozzle pressure in relay "B" decreases, causing the cylinder pressure below the piston to similarly decrease. The unbalanced pressures acting on the piston cause it to move downwards to change the valve plug position. The movement 11-128

of the piston is fed back to the beam by means of a range spring connected between the beam and an extension of the piston rod. This arrangement provides feed-back to the system to prevent over-correction and ensures a definite position for the piston for every value of instrument signal.

\.._)

_NVTIIGtW.

.......

....

tul'll'LV I'I'8IUIIIE

~

lWCY1JNDEIII NrDfJIE

~

IImTOII C'n.H)IJI P'IIDIUIE

_NOZZL.!:~

Fig. 7.13 )

Schematic

illustration

of a piston

actuator

Piston actuators can be arranged to either move the valve stem up or down on increasing instrument signal, depending on the positi~n of the instrument bellows. In order to move the piston to a desired safe position in the event of air supp'ly failure, piston actuators may be fitted wit has p r ing tor e turn' the act u a tor stem tot he up 0 r down position. This has a disadvantage however of absorbing a certain amount of available thrust in compressing the spring. It is also possible to fit pneumatic tripping devices with air pressure stored in capacity chambers, which can be switched to either move the piston to the up or down position in the event of air failure, or to fit a device which locks the piston in the last controlled position. 11-129

As with handwheels during (3) with

to piston

start-up

or emergency

Electric

actuators

gear

trains They

often

feed-back

are quite

with

and have

long

for very

large

Closely electricity

in last limit

stroke connected

in response

Fig.

7.14

range

locations

to diaphragm The

position,

switches

the valve

and

where

service,

but can

or fail

which

be

of a potentiometric actuators

fail-safe

torque

no other actuators

and piston

only

motor

of output

of electric

on/off

fix,

action one.

limiting

makes

They

devices

them-suitable

valves. to the electric

type

supply

a wide

the addition

capabilities,

butterfly

electro-hydraulic

with

position

of an electric

in remote only

to fit

conditions.

consist

in operation.

is a lock

be fitted

control

Relative

slow

shutdown

The majority

control

device.

available

used

requiring

for modulating

to manually

to provide

is available.

for valves

it is possible

usually

arranged

are

source

are used

can

actuators

actuators

power

they

actuators,

Electric

forces.

used

diaphragm

(Fig.7.14)

but which

will

to a milliamp

which

again

produce signal

An electro-hydraul 11-130

actuators

are

only

excellent source.

ie actuator

the

need

an

throttling

An

electric

pressure

motor

to a piston,

to the pneumatic (4)

is connected

Actuator .The choice

piston

which

to a pump is positiqned

in response

feeding

oil

in a similar

to the control

at high manner

signal.

selection of actuator

for a specific

application

wil I be

dependent upon various factors. 1. The power source available. 2. Fail safe requirements. 3. Force requirements of the valve. 4. Form of control required. 5. Cost. Power source Most plants have both compressed air arid electricity available on site, but there are occasions where the site is in a remote location, and it is uneconomic to install an air compressor. This will automatically cut down the choice to either electric or electro-hydraulic. 1)

2)

.~

J

Fail safe requirements Although both pneumatic and electrical systems are very reliable, it is always necessary to consider the effect of the loss of the power source, which could result in a hazardous sitation developing. By storing energy in springs or in pneumatic capacity chambers, this reserve power can be cal led upon to move the valve to its safe position when the main power .sou rce fail s • Th e t h re e f a i Iu re rnodes ava i1ab 1ear e : f a i I-0 pen, fail-close, or fail-fixed which locks the valve in its last controlled position. Force requirements of .the valve An actuator must have sufficient output thrust to handle the requirements of the valve, although it is obviously uneconomic to fit an actuator which is over-powered~ It has to be capable of closing the valve under all possible service conditions. There is usually a wide choice of sizes available for all types of actuators from pneumatic spring and diaphragm 3)

11-131

through

to electro-hydraulic,

is usually

best

left

one most

suited

4}

of control

Form The

form

to the particular

of control

either

or maximum

possess

sufficient has

controller, achieve with

this

as a relay

not

normally

valve

considering travel type 5}

be considered,

unless

faster

special

speeds

are

the To

device

such

and

stroking

speed or open

conditions. actuator

the spring

relays

Here

compatible

to close

the piston

than

booster

although

in emergency

actuators,

to

from

of vibration

be necessary

or two seconds

pneumatic

at much

the effects

so

the process.

intermediate

and

has

selection.

be directly

be added.

and

in signal

monitoring

must

of

the valve.

change

or some

it may

It merety careful

either

signals

instrument,

open

more

to every

signal,

also

one

much

must

a problem,

within

and

is c~ntinuously

of action

must

the

(on/off)

receive

simple.

to close

or positioner

temperature

actuators

is fairly

the actuator

speed

choose

two position

the controlling

require

the controlling The

from

to respond

which

will

of size

valve.

On/off

force

actuators

the actuator

who

can be either

of actuator

Throttling

selection

reqUired

(throttling).

the choice

the actual

to the manufacturer

or analogue zero

and

is a

~en

will

and diaphragm

installed.

Cost The

factor

cost

of an actuator

in its selection.

the most

economical,

maintenance, capability

~ere

both

of this

Electric

type

often

the over-riding

compressed

in initial

is the diaphragm

is the piston

cost

actuator.

air and

subsequent

~ere

is insufficient,

is available, the thrust

the next

best

choice

actuator. or electro-hydraulic

considered

when

high

is required,

force

is very

compressed

air

which

actuators is not

available

el"iminates

11-132

should

only

or when

~he pneumatic

be a very

type.

Chapter

8

GAS CHROMATOGRAPHY

Perphaps more than any other technique of instrumental analysis gas chromatography has proved to be of critical importance in many industries and disciplines. Gas chromatography is a type of partition chromatography, similar in many ways to other techniques of this kind such as liquid chromatography, paper chromatography, etc. The distinguishing features of gas chromatography are that the mobile phase is a gas and that the rnat ion 0 f the c omp 0 nen t ban ds , inth e d ire c tion 0 f "ch roma tog rap h i c de vel 0 pme n t ", i nvol ve s the for ce d diffusion of the respective substances in their vapour phases. Many of the differences between for example liquid chromatography and gas chromatography are due to the physical properties of the mobile phase - for instance its viscosity, acidity and compressibility. The basi~ for differential zone-migration remains the same: two components will migrate at different rates in the same chromatographic system if their distribution constants are different. Fig.B.I shows a block diagram schematic of a dual-column gas chromatograph showing the essential parts. A large number of methods of detection of the e Iu ted comp one'nts from gas chroma tograpby co Iumns .ex ist. The thermal conductivity (hot wire) detector was one of the earlier forms employed although in widespread use is also the flame ionisation detector. A very sensitive and selective detector is the electron capture detector. These three types of detector are illustrated in Fig.8.2. As an .example of performance for modern gas chromatography Fig ..8.3 shows chromatograms obtained for a standard mixture of polycyclic aromatic hydrocarbons and of a coke-furnace emission.

11-133

._------------_._---_.

__ .

Automation

of Analytical

Instrumentation.

are generally

classed

on the nature

of their

some

or chemical

physical

sample

yielding

discrete

only

principles include receiving uncontrol

works

after

provision

is a smooth

upon

a batch-loaded

each

batch.

or control

A clear automated

devices.

performed

at given curve

For

instrument

conditions

observing

function

senses the

of time.

sample

A

and supplies

derives

its operating

procedures

and must

unattended

selective

depending

operation:

chemical

analyses

and conmunicating

under

with

equipment.

distinction

intervention.

analytical

performing

led enviromental

Each

instruments

(batch)

by directly

that

for continuous

samples,

or discrete A continuous

property

from conventional

monitoring

titration

operation.

an output

instrument

information

as continuous

Automated

should

Automatic points

devices

between cause

in the operation

instance,

or simply

be made

an automatic

stops

a titration

automatic

required without titrator

and

acts

to be

human records

at an end

point

a by

mechanical or electrical means (such as a relay) instead of manually. Automated deVices, on the other hand, replace human manipulative effort by mechanical and instrumental devices regulated by feedback of information; thus the apparatus is self-monitoring or self-balancing. An automated titrator may be intended to maintain a sample at some preselected (set point) state, for example pH ; 8. To do this the pH of the solution is sensed and compared to a set point of pH 8 and acid or base is added continuously to keep the sample pH at the set point. In the past automated instruments were not well accepted because of their limited capability and reliability. However, because of the increased complexity and number of clinical, industrial and other types of samples requiring analysis, classical (n~automated) techniques, as well as automated techniques, have been improved in capability. We'll established instruments such as infrared analysers, gas chromatographs, ion-selective electrode systems and automatic wet-chemical analysers can now measure quite complex species and mixtures. Reliability has also increased because the maturity of 11-134·

De te c tor Block

Column

A

Pit· "sure Reduction Valve

Injection Port ~ ........... __,Ior Column B

Injection Port fOT Column A L-.-......__...... Helium

Me.tering Valves for Columns A and B

Tank

Fig. 8.1

Block diagram chromatograph

of a dual-column gas showing essential parts

11-135

Cross-section of a typical four-wire conductivity cell. Courtesy of Gow-Mac Instrument Co. Top View Outlet

Dullel

L

_j

r

I

"Inlet

tnlet

Side View

Exl13ust

Ourle.

Cap

Collector

A flameionization detector.

FlO A~tmbly

A "pin-cup" design for

'Column

~;1'V('X'Jo.~

electron-capture detection, in cross-section.

Fig.

8.2

Some configurations of detector assembly for gas chromatography 11-136

Co 11eel or Electrode

I

I

I

I

I

I

T

T

Q)

r.J>

~

0 0.. U)

Q.)

~

~ ~c ......

0

~

C)

C"I

~

ca

.__

r-l'O

r-:-I

~ ~

s

C

-a r-l00

.,-l

Q)

("I")H

:S la

...... ca .__

/

.u

.. 28

26

24

~

~

.-;

ro ...... o ...... N

~

_,..)

\...t

s

~0

t\I \::

C!I

r'

c

r-l

I'tj

m

.-l

Q)

s::

.s.

.c ~

.. s::

1

I

I

Q)

Q)

0

Q)

§

e tB

~~ roe

Q)

o

'?

0.

~'Ero

l!')

~

§ ..-;

~:>.

(])

I

Aroma tics

Benz (a) anthracene

Q)

Q)

c Q)

~~

l.-.

v

Q)

I

r

Blend of Six Polynuclear

22

~f 20

18

•

I

16

14

_j

12

10

I

j_

8

6

1 4

2

Time, mi n

(l)

r.J>

C

a

0.. U)

~ ~ a ~ o Q.) ~
Chromatogram QJ

cQJ N C

-

.3 ~'B ca r-I

>< c Q)

+J 00

of Coke Oven Effluent Benz (c) acridine

Q)

C

(IJ

~>.

5

Q)

Q)

c

-Q)

0"

rotl

-ca ~ N.c:

~.

§

113

~

C.JJ

{Sa

~

.,-l

~

tIl

..

("I")

Q

34 32 30

28 26 24 22

20

18

16

14

12 10

8

6

4

Time, mi n

Fig. 8.3

Chromatograms of a standard mixture of polycyclic aromatic hydrocarbons and a coke-furnace emission

11-137

2

solid-state equipment The sections is largely

electronics

has brought

easier

data

handling

and

maintenance. chemical

instrumentation

can all be utilised dictated

discussed

in automated

by economics

and

in the preceding systems.

the applicability

The

choice of an

would be difficult to review all of the instrumental systems used in automated control in the space available. Spectroscopic electrochemical and chromatographic systems are the most widely employed and a review of the principles of operation of these has been have drawn here extensively presented here in small compass. on several standard texts concerned with instrumental analYSis - notably 'Instrumental Analysis· by Bauer, Christian and Q'Reilley. I gratefully acknowledge their permission to quote from this work and to reproduce diagrams from this text. instrument

to the proposed

problem.

It

'.----._/

II-138

Chapter

9

TELEMETRY APPLICATIONS

The conmunications requirements of distributed control networks, incentives for plant-wide automation, and desire to establish unattended remotely-controlled facilities for applications sUch as offshore production and processing are making it helpful for instrumentation specialists to become conversant in telemetry and other forms of signal transmission. At the same time, advances are being made in telemetry that extend the range and flexibility of the systems that can be implemented. Utilities applications Utilities have been traditional industrial users of telemetry systems, principally owing to the need to monitor and control distribution systems over large geographical areas. Allocation of 20 new frequency pairs by the FCC for utility distribution automation should further increase use of fixed two-way radio telemetry for those applications, asserted Michael Berlin of Motorola Fixed Products Division. In a telemetry system designed for the Columbus OH water distribution network, emphasis was placed on selecting signal transmission media. The final design involved a combination of leased telephone lines for connection to each remote site with microwaves and a city-owned cable for multi-channel communications, noted Terrance Brueck of Bv1A lnc, and John R. Doutt of the City of Columbus. UHF radio was considered to -avoid the line-of-sight limiiations of microwave transmission, but was rejected because of restricted channel capacity. Control of underground petroleum product storage faci lities presented more complex utility telemetry requirements. One such facility, locate~ near Houston, provides high pressure storage I 1-1·39

for natural demand

peaks.

Houston

gas

and The

professional

is employed

primarily

instrumentation, engineer,

the processes

used

to inject

and operation

of the automatic

as a source

explained.

provides

supervisory

and withdraw safety

Michael

gas,

data

to meet Felt,

control

a of

acquisition,

systems.

The facility

can operate unattended since the telemetry system allows the station operator to monitor and control the process from a central point, detect incipient problems, and take corrective action before the computer generates an alarm signal or shutdown sequence. When people are on-site, the s.upervisory system allows them to move freely through the plant to check the performance of various functions . .Ate Iernetry -0 r i en ted i.nteg rat ed sy stem comb i n i n g load management and supervisory control and data acquisition systems offers the potential for significant savings in electricity distribution networks. Integrating the functions not only saves money in equipment cost, but also enhances performance through a higher degree of synchronization than is practical using stand-alone systems, explained Robert Morris and Philip Pennington of Tejas Controls. The proposed approach uses closed loop control with demand feedback, to defer energy use by consumer applicances in a manner that minimizes peak consumption rates. The system activates and shuts down water heaters, air conditions, irrigation pumps, and other loads whose operation may be easily deferred. Sophisticated telemetry is needed to prevent communication path interference and contention, synchronize load shedding and restoration, and coordinate i~dividual operations with the overall regional power demand. As an example, Mr. Morris and Mr. Pennington explained that time and duration of load reduction is conveyed by digital messages over a combination of voice grade telephone lines and ~ radio channels. Addressable load groups are time-synchronized for various transmitters to ensure that receivers react to the intended commands, even though adjacent users are tuned to the same 'frequency. Communication error checking is performed at several levels, with security codes available in the protocol between the master and the remote terminal units.

0--

11-140

/

JEX NOEX JVPC.pdf

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